Academic Appointments


Honors & Awards


  • Rolex Award for Enterprise, Rolex (2012)
  • Walter B. Cannon Award, American Physiological Society (2008)
  • Pew Marine Conservation Fellow, Pew Foundation (1997)
  • MacArthur Fellow, MacArthur Foundation (1996)
  • Presidents Medal, Society for Experimental Biology, London (1994)
  • Presidential Young Investigator Award, National Science Foundation (1989)

Professional Education


  • B.A., University of Vermont, Zoology (1980)
  • Ph.D, Duke University, Zoology (1986)

Current Research and Scholarly Interests


Thermal physiology, open ocean predators, ecological physiology and tuna biology

2020-21 Courses


Stanford Advisees


All Publications


  • Mitochondrial genome of the silky sharkCarcharhinus falciformisfrom the British Indian Ocean Territory Marine Protected Area MITOCHONDRIAL DNA PART B-RESOURCES Johri, S., Chapple, T. K., Dinsdale, E. A., Robert, S., Block, B. A. 2020; 5 (3): 2416–17
  • Mitochondrial genome of the Silvertip shark, Carcharhinus albimarginatus, from the British Indian Ocean Territory MITOCHONDRIAL DNA PART B-RESOURCES Johri, S., Dunn, N., Chapple, T. K., Curnick, D., Savolainen, V., Dinsdale, E. A., Block, B. A. 2020; 5 (3): 2085–86
  • Complete mitochondrial genome of the gray reef shark, Carcharhinus amblyrhynchos (Carcharhiniformes: Carcharhinidae) MITOCHONDRIAL DNA PART B-RESOURCES Dunn, N., Johri, S., Curnick, D., Carbone, C., Dinsdale, E. A., Chapple, T. K., Block, B. A., Savolainen, V. 2020; 5 (3): 2080–82
  • Complete mitochondrial genome of the whitetip reef shark Triaenodon obesus from the British Indian Ocean Territory Marine Protected Area MITOCHONDRIAL DNA PART B-RESOURCES Johri, S., Chapple, T. K., Robert, S., Dinsdale, E. A., Block, B. A. 2020; 5 (3): 2347–49
  • Biomechanical Analysis of the Slow-Twitch (Red) Muscle Force Transmission Pathways in Tunas. Physiological and biochemical zoology : PBZ Cromie Lear, M. J., Millard, M., Gleiss, A. C., Dale, J., Dimitrov, M., Peiros, E., Block, B. ; 93 (3): 185–98

    Abstract

    In tunas, the slow-twitch red muscle, which has an elevated temperature, powers thunniform locomotion, a stiff-bodied swimming style. The anatomical placement and operating temperatures of red muscle vary widely among teleosts: in tunas, the red muscle is located centrally in the body, adjacent to the spine, and maintains an elevated temperature. In the majority of ectothermic teleosts, red muscle is located laterally in the body, adjacent to the skin, and operates at ambient temperature. The specialized physiology and biomechanics of red muscle in tunas are often considered important adaptations to their high-performance pelagic lifestyle; however, the mechanics of how muscular work is transmitted to the tail remains largely unknown. The red muscle has a highly pennate architecture and is connected to the spine through a network of bones (epicentral bones) and long tendons (posterior oblique tendons). The network of long tendons has been hypothesized to enhance the power transmitted to the tail. Here, we investigate the morphology and biomechanics of the tuna's red muscle and tendons to determine whether elasticity is exploited to reduce the cost of transport, as is the case in many terrestrial vertebrates. To address this question, we evaluate two hypotheses: (1) tendons stretch during red-muscle-actuated swimming and (2) tendons comprise the primary load transmission pathway from the red muscle to the spine. To evaluate these hypotheses, we measured the mechanical properties of the posterior oblique tendons and performed novel dissections to estimate the peak force that the red muscle can generate. The force-generating capacity of the red muscle is calculated to be much greater than the load-bearing capacity of the posterior oblique tendons. Thus, the long tendons likely stretch under force from the red muscle, but they are not strong enough to be the primary force transmission pathway. These results suggest that other pathways, such as serial load transmission through the red muscle myomeres to the great lateral tendon and/or the anterior oblique tendons to the skin, transmit appreciable force to the tail.

    View details for DOI 10.1086/708247

    View details for PubMedID 32196408

  • Shark movement strategies influence poaching risk and can guide enforcement decisions in a large, remote marine protected area JOURNAL OF APPLIED ECOLOGY Jacoby, D. P., Ferretti, F., Freeman, R., Carlisle, A. B., Chapple, T. K., Curnick, D. J., Dale, J. J., Schallert, R. J., Tickler, D., Block, B. A. 2020
  • Individual variation in residency and regional movements of reef manta rays Mobula alfredi in a large marine protected area MARINE ECOLOGY PROGRESS SERIES Andrzejaczek, S., Chapple, T. K., Curnick, D. J., Carlisle, A. B., Castleton, M., Jacoby, D. P., Peel, L. R., Schallert, R. J., Tickler, D. M., Block, B. A. 2020; 639: 137–53

    View details for DOI 10.3354/meps13270

    View details for Web of Science ID 000525359900009

  • Shark fin trade bans and sustainable shark fisheries CONSERVATION LETTERS Ferretti, F., Jacoby, D. P., Pfleger, M. O., White, T. D., Dent, F., Micheli, F., Rosenberg, A. A., Crowder, L. B., Block, B. A. 2020

    View details for DOI 10.1111/conl.12708

    View details for Web of Science ID 000512962900001

  • Skeletal muscle and cardiac transcriptomics of a regionally endothermic fish, the Pacific bluefin tuna, Thunnus orientalis. BMC genomics Ciezarek, A., Gardner, L., Savolainen, V., Block, B. 2020; 21 (1): 642

    Abstract

    The Pacific bluefin tuna (Thunnus orientalis) is a regionally endothermic fish that maintains temperatures in their swimming musculature, eyes, brain and viscera above that of the ambient water. Within their skeletal muscle, a thermal gradient exists, with deep muscles, close to the backbone, operating at elevated temperatures compared to superficial muscles near the skin. Their heart, by contrast, operates at ambient temperature, which in bluefin tunas can range widely. Cardiac function in tunas reduces in cold waters, yet the heart must continue to supply blood for metabolically demanding endothermic tissues. Physiological studies indicate Pacific bluefin tuna have an elevated cardiac capacity and increased cold-tolerance compared to warm-water tuna species, primarily enabled by increased capacity for sarcoplasmic reticulum calcium cycling within the cardiac muscles.Here, we compare tissue-specific gene-expression profiles of different cardiac and skeletal muscle tissues in Pacific bluefin tuna. There was little difference in the overall expression of calcium-cycling and cardiac contraction pathways between atrium and ventricle. However, expression of a key sarcoplasmic reticulum calcium-cycling gene, SERCA2b, which plays a key role maintaining intracellular calcium stores, was higher in atrium than ventricle. Expression of genes involved in aerobic metabolism and cardiac contraction were higher in the ventricle than atrium. The two morphologically distinct tissues that derive the ventricle, spongy and compact myocardium, had near-identical levels of gene expression. More genes had higher expression in the cool, superficial muscle than in the warm, deep muscle in both the aerobic red muscle (slow-twitch) and anaerobic white muscle (fast-twitch), suggesting thermal compensation.We find evidence of widespread transcriptomic differences between the Pacific tuna ventricle and atrium, with potentially higher rates of calcium cycling in the atrium associated with the higher expression of SERCA2b compared to the ventricle. We find no evidence that genes associated with thermogenesis are upregulated in the deep, warm muscle compared to superficial, cool muscle. Heat generation may be enabled by by the high aerobic capacity of bluefin tuna red muscle.

    View details for DOI 10.1186/s12864-020-07058-z

    View details for PubMedID 32942994

  • Tracking the response of industrial fishing fleets to large marine protected areas in the Pacific Ocean. Conservation biology : the journal of the Society for Conservation Biology White, T. D., Ong, T., Ferretti, F., Block, B. A., McCauley, D. J., Micheli, F., De Leo, G. A. 2020

    Abstract

    Large marine protected areas (MPAs) of unprecedented size have recently been established across the global oceans, yet their ability to meet conservation objectives is debated. Key areas of debate include uncertainty over nations' abilities to enforce fishing bans across vast, remote regions and the intensity of human impacts before and after MPA implementation. We used a recently developed vessel tracking data set (produced using Automatic Identification System detections) to quantify the response of industrial fishing fleets to 5 of the largest MPAs established in the Pacific Ocean since 2013. After their implementation, all 5 MPAs successfully kept industrial fishing effort exceptionally low. Detected fishing effort was already low in 4 of the 5 large MPAs prior to MPA implementation, particularly relative to nearby regions that did not receive formal protection. Our results suggest that these large MPAs may present major conservation opportunities in relatively intact ecosystems with low immediate impact to industrial fisheries, but the large MPAs we considered often did not significantly reduce fishing effort because baseline fishing was typically low. It is yet to be determined how large MPAs may shape global ocean conservation in the future if the footprint of human influence continues to expand. Continued improvement in understanding of how large MPAs interact with industrial fisheries is a crucial step toward defining their role in global ocean management.

    View details for DOI 10.1111/cobi.13584

    View details for PubMedID 33031635

  • Abundance and distribution of the white shark in the Mediterranean Sea FISH AND FISHERIES Moro, S., Jona-Lasinio, G., Block, B., Micheli, F., De Leo, G., Serena, F., Bottaro, M., Scacco, U., Ferretti, F. 2019

    View details for DOI 10.1111/faf.12432

    View details for Web of Science ID 000504574900001

  • Size-specific apparent survival rate estimates of white sharks using mark-recapture models CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Kanive, P. E., Rotella, J. J., Jorgensen, S. J., Chapple, T. K., Hines, J. E., Anderson, S. D., Block, B. A. 2019; 76 (11): 2027–34
  • Cardiac remodeling in response to embryonic crude oil exposure involves unconventional NKX family members and innate immunity genes. The Journal of experimental biology Gardner, L. D., Peck, K. A., Goetz, G. W., Linbo, T. L., Cameron, J., Scholz, N. L., Block, B. A., Incardona, J. P. 2019

    Abstract

    Cardiac remodeling results from both physiological and pathological stimuli. Compared to mammals, fish hearts show a broader array of remodeling changes in response to environmental influences, providing exceptional models for dissecting the molecular and cellular bases of cardiac remodeling. We recently characterized a form of pathological remodeling in juvenile pink salmon (Oncorhynchus gorbuscha) in response to crude oil exposure during embryonic cardiogenesis. In the absence of overt pathology (cardiomyocyte death or inflammatory infiltrate), cardiac ventricles in exposed fish showed altered shape, reduced thickness of compact myocardium, and hypertrophic changes in spongy, trabeculated myocardium. Here we used RNA sequencing to characterize molecular pathways underlying these defects. In juvenile ventricular cardiomyocytes, antecedent embryonic oil exposure led to dose-dependent up-regulation of genes involved in innate immunity and two NKX homeobox transcription factors not previously associated with cardiomyocytes, nkx2.3 and nkx3.3 Absent from mammalian genomes, the latter is largely uncharacterized. In zebrafish embryos nkx3.3 demonstrated a potent effect on cardiac morphogenesis, equivalent to nkx2.5, the primary transcription factor associated with ventricular cardiomyocyte identity. The role of nkx3.3 in heart growth is potentially linked to the unique regenerative capacity of fish and amphibians. Moreover, these findings support a cardiomyocyte-intrinsic role for innate immune response genes in pathological hypertrophy. This study demonstrates how an expanding mechanistic understanding of environmental pollution impacts - i.e., the chemical perturbation of biological systems - can ultimately yield new insights into fundamental biological processes.

    View details for DOI 10.1242/jeb.205567

    View details for PubMedID 31597731

  • The importance of migratory connectivity for global ocean policy. Proceedings. Biological sciences Dunn, D. C., Harrison, A., Curtice, C., DeLand, S., Donnelly, B., Fujioka, E., Heywood, E., Kot, C. Y., Poulin, S., Whitten, M., Akesson, S., Alberini, A., Appeltans, W., Arcos, J. M., Bailey, H., Ballance, L. T., Block, B., Blondin, H., Boustany, A. M., Brenner, J., Catry, P., Cejudo, D., Cleary, J., Corkeron, P., Costa, D. P., Coyne, M., Crespo, G. O., Davies, T. E., Dias, M. P., Douvere, F., Ferretti, F., Formia, A., Freestone, D., Friedlaender, A. S., Frisch-Nwakanma, H., Frojan, C. B., Gjerde, K. M., Glowka, L., Godley, B. J., Gonzalez-Solis, J., Granadeiro, J. P., Gunn, V., Hashimoto, Y., Hawkes, L. M., Hays, G. C., Hazin, C., Jimenez, J., Johnson, D. E., Luschi, P., Maxwell, S. M., McClellan, C., Modest, M., Notarbartolo di Sciara, G., Palacio, A. H., Palacios, D. M., Pauly, A., Rayner, M., Rees, A. F., Salazar, E. R., Secor, D., Sequeira, A. M., Spalding, M., Spina, F., Van Parijs, S., Wallace, B., Varo-Cruz, N., Virtue, M., Weimerskirch, H., Wilson, L., Woodward, B., Halpin, P. N. 2019; 286 (1911): 20191472

    Abstract

    The distributions of migratory species in the ocean span local, national and international jurisdictions. Across these ecologically interconnected regions, migratory marine species interact with anthropogenic stressors throughout their lives. Migratory connectivity, the geographical linking of individuals and populations throughout their migratory cycles, influences how spatial and temporal dynamics of stressors affect migratory animals and scale up to influence population abundance, distribution and species persistence. Population declines of many migratory marine species have led to calls for connectivity knowledge, especially insights from animal tracking studies, to be more systematically and synthetically incorporated into decision-making. Inclusion of migratory connectivity in the design of conservation and management measures is critical to ensure they are appropriate for the level of risk associated with various degrees of connectivity. Three mechanisms exist to incorporate migratory connectivity into international marine policy which guides conservation implementation: site-selection criteria, network design criteria and policy recommendations. Here, we review the concept of migratory connectivity and its use in international policy, and describe the Migratory Connectivity in the Ocean system, a migratory connectivity evidence-base for the ocean. We propose that without such collaboration focused on migratory connectivity, efforts to effectively conserve these critical species across jurisdictions will have limited effect.

    View details for DOI 10.1098/rspb.2019.1472

    View details for PubMedID 31551061

  • A rapid environmental DNA method for detecting white sharks in the open ocean METHODS IN ECOLOGY AND EVOLUTION Truelove, N. K., Andruszkiewicz, E. A., Block, B. A. 2019; 10 (8): 1128–35
  • Animal-Borne Telemetry: An Integral Component of the Ocean Observing Toolkit FRONTIERS IN MARINE SCIENCE Harcourt, R., Sequeira, A. M., Zhang, X., Roquet, F., Komatsu, K., Heupel, M., McMahon, C., Whoriskey, F., Meekan, M., Carroll, G., Brodie, S., Simpfendorfer, C., Hindell, M., Jonsen, I., Costa, D. P., Block, B., Muelbert, M., Woodward, B., Weise, M., Aarestrup, K., Biuw, M., Boehme, L., Bograd, S. J., Cazau, D., Charrassin, J., Cooke, S. J., Cowley, P., de Bruyn, P., du Dot, T., Duarte, C., Eguiluz, V. M., Ferreira, L. C., Fernandez-Gracia, J., Goetz, K., Goto, Y., Guinet, C., Hammill, M., Hays, G. C., Hazen, E. L., Huckstadt, L. A., Huveneers, C., Iverson, S., Jaaman, S., Kittiwattanawong, K., Kovacs, K. M., Lydersen, C., Moltmann, T., Naruoka, M., Phillips, L., Picard, B., Queiroz, N., Reverdin, G., Sato, K., Sims, D. W., Thorstad, E. B., Thums, M., Treasure, A. M., Trites, A. W., Williamss, G. D., Yonehara, Y., Fedak, M. A. 2019; 6
  • Estimating Space Use of Mobile Fishes in a Large Marine Protected Area With Methodological Considerations in Acoustic Array Design FRONTIERS IN MARINE SCIENCE Carlisle, A. B., Tickler, D., Dale, J. J., Ferretti, F., Curnick, D. J., Chapple, T. K., Schallert, R. J., Castleton, M., Block, B. A. 2019; 6
  • Temperature dependent pre- and postprandial activity in Pacific bluefin tuna (Thunnus orientalis) COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY Gleiss, A. C., Dale, J. J., Klinger, D. H., Estess, E. E., Gardner, L. D., Machado, B., Norton, A. G., Farwell, C., Block, B. A. 2019; 231: 131–39
  • Direct measurement of swimming and diving kinematics of giant Atlantic bluefin tuna (Thunnus thynnus) ROYAL SOCIETY OPEN SCIENCE Gleiss, A. C., Schallert, R. J., Dale, J. J., Wilson, S. G., Block, B. A. 2019; 6 (5): 190203

    Abstract

    Tunas possess a range of physiological and mechanical adaptations geared towards high-performance swimming that are of considerable interest to physiologists, ecologists and engineers. Advances in biologging have provided significant improvements in understanding tuna migrations and vertical movement patterns, yet our understanding of the locomotion and swimming mechanics of these fish under natural conditions is limited. We equipped Atlantic bluefin tuna (Thunnus thynnus) with motion-sensitive tags and video cameras to quantify the gaits and kinematics used by wild fish. Our data reveal significant variety in the locomotory kinematics of Atlantic bluefin tuna, ranging from continuous locomotion to two types of intermittent locomotion. The tuna sustained swimming speeds in excess of 1.5 m s-1 (0.6 body lengths s-1), while beating their tail at a frequency of approximately 1 Hz. While diving, some descents were entirely composed of passive glides, with slower descent rates featuring more gliding, while ascents were primarily composed of active swimming. The observed swimming behaviour of Atlantic bluefin tuna is consistent with theoretical models predicting such intermittent locomotion to result in mechanical and physiological advantages. Our results confirm that Atlantic bluefin tuna possess behavioural specializations to increase their locomotory performance, which together with their unique physiology improve their capacity to use pelagic and mesopelagic habitats.

    View details for DOI 10.1098/rsos.190203

    View details for Web of Science ID 000470127300046

    View details for PubMedID 31218059

    View details for PubMedCentralID PMC6549966

  • Cryptic habitat use of white sharks in kelp forest revealed by animal-borne video. Biology letters Jewell, O. J., Gleiss, A. C., Jorgensen, S. J., Andrzejaczek, S., Moxley, J. H., Beatty, S. J., Wikelski, M., Block, B. A., Chapple, T. K. 2019; 15 (4): 20190085

    Abstract

    Traditional forms of marine wildlife research are often restricted to coarse telemetry or surface-based observations, limiting information on fine-scale behaviours such as predator-prey events and interactions with habitat features. We use contemporary animal-attached cameras with motion sensing dataloggers, to reveal novel behaviours by white sharks, Carcharodon carcharias, within areas of kelp forest in South Africa. All white sharks tagged in this study spent time adjacent to kelp forests, with several moving throughout densely kelp-covered areas, navigating through channels and pushing directly through stipes and fronds. We found that activity and turning rates significantly increased within kelp forest. Over 28 h of video data revealed that white shark encounters with Cape fur seals, Arctocephalus pusillus pusillus, occurred exclusively within kelp forests, with seals displaying predator evasion behaviour during those encounters. Uniquely, we reveal the use of kelp forest habitat by white sharks, previously assumed inaccessible to these large predators.

    View details for PubMedID 30940023

  • Killer whales redistribute white shark foraging pressure on seals SCIENTIFIC REPORTS Jorgensen, S. J., Anderson, S., Ferretti, F., Tietz, J. R., Chapple, T., Kanive, P., Bradley, R. W., Moxley, J. H., Block, B. A. 2019; 9
  • Killer whales redistribute white shark foraging pressure on seals. Scientific reports Jorgensen, S. J., Anderson, S., Ferretti, F., Tietz, J. R., Chapple, T., Kanive, P., Bradley, R. W., Moxley, J. H., Block, B. A. 2019; 9 (1): 6153

    Abstract

    Predatory behavior and top-down effects in marine ecosystems are well-described, however, intraguild interactions among co-occurring marine top predators remain less understood, but can have far reaching ecological implications. Killer whales and white sharks are prominent upper trophic level predators with highly-overlapping niches, yet their ecological interactions and subsequent effects have remained obscure. Using long-term electronic tagging and survey data we reveal rare and cryptic interactions between these predators at a shared foraging site, Southeast Farallon Island (SEFI). In multiple instances, brief visits from killer whales displaced white sharks from SEFI, disrupting shark feeding behavior for extended periods at this aggregation site. As a result, annual predations of pinnipeds by white sharks at SEFI were negatively correlated with close encounters with killer whales. Tagged white sharks relocated to other aggregation sites, creating detectable increases in white shark density at Ano Nuevo Island. This work highlights the importance of risk effects and intraguild relationships among top ocean predators and the value of long-term data sets revealing these consequential, albeit infrequent, ecological interactions.

    View details for PubMedID 30992478

  • Cryptic habitat use of white sharks in kelp forest revealed by animal-borne video BIOLOGY LETTERS Jewell, O. D., Gleiss, A. C., Jorgensen, S. J., Andrzejaczek, S., Moxley, J. H., Beatty, S. J., Wikelski, M., Block, B. A., Chapple, T. K. 2019; 15 (4)
  • Estimating Natural Mortality of Atlantic Bluefin Tuna Using Acoustic Telemetry SCIENTIFIC REPORTS Block, B. A., Whitlock, R., Schallert, R. J., Wilson, S., Stokesbury, M. W., Castleton, M., Boustany, A. 2019; 9
  • Estimating Natural Mortality of Atlantic Bluefin Tuna Using Acoustic Telemetry. Scientific reports Block, B. A., Whitlock, R., Schallert, R. J., Wilson, S., Stokesbury, M. J., Castleton, M., Boustany, A. 2019; 9 (1): 4918

    Abstract

    Atlantic bluefin tuna (Thunnus thynnus) are highly migratory fish with a contemporary range spanning the North Atlantic Ocean. Bluefin tuna populations have undergone severe decline and the status of the fish within each population remains uncertain. Improved biological knowledge, particularly of natural mortality and rates of mixing of the western (GOM) and eastern (Mediterranean) populations, is key to resolving the current status of the Atlantic bluefin tuna. We evaluated the potential for acoustic tags to yield empirical estimates of mortality and migration rates for long-lived, highly migratory species such as Atlantic bluefin tuna. Bluefin tuna tagged in the Gulf of St. Lawrence (GSL) foraging ground (2009-2016) exhibited high detection rates post release, with 91% crossing receiver lines one year post tagging, 61% detected after year two at large, with detections up to ~1700 days post deployment. Acoustic detections per individual fish ranged from 3 to 4759 receptions. A spatially-structured Bayesian mark recapture model was applied to the acoustic detection data for Atlantic bluefin tuna electronically tagged in the GSL to estimate the rate of instantaneous annual natural mortality. We report a median estimate of 0.10yr-1 for this experiment. Our results demonstrate that acoustic tags can provide vital fisheries independent estimates for life history parameters critical for improving stock assessment models.

    View details for PubMedID 30894557

  • Predicted hotspots of overlap between highly migratory fishes and industrial fishing fleets in the northeast Pacific. Science advances White, T. D., Ferretti, F., Kroodsma, D. A., Hazen, E. L., Carlisle, A. B., Scales, K. L., Bograd, S. J., Block, B. A. 2019; 5 (3): eaau3761

    Abstract

    Many species of sharks and some tunas are threatened by overexploitation, yet the degree of overlap between industrial fisheries and pelagic fishes remains poorly understood. Using satellite tracks from 933 industrial fishing vessels and predictive habitat models from 876 electronic tags deployed on seven shark and tuna species, we developed fishing effort maps across the northeast Pacific Ocean and assessed overlap with core habitats of pelagic fishes. Up to 35% of species' core habitats overlapped with fishing effort. We identified overlap hotspots along the North American shelf, the equatorial Pacific, and the subtropical gyre. Results indicate where species require international conservation efforts and effective management within national waters. Only five national fleets (Mexico, Taiwan, China, Japan, and the United States) account for >90% of overlap with core habitats of our focal sharks and tunas on the high seas. These results inform global negotiations to achieve sustainability on the high seas.

    View details for PubMedID 30891492

  • Predicted hotspots of overlap between highly migratory fishes and industrial fishing fleets in the northeast Pacific SCIENCE ADVANCES White, T. D., Ferretti, F., Kroodsma, D. A., Hazen, E. L., Carlisle, A. B., Scales, K. L., Bograd, S. J., Block, B. A. 2019; 5 (3)
  • Population connectivity of pelagic megafauna in the Cuba-Mexico-United States triangle SCIENTIFIC REPORTS Rooker, J. R., Dance, M. A., Wells, R., Ajemian, M. J., Block, B. A., Castleton, M. R., Drymon, J., Falterman, B. J., Franks, J. S., Hammerschlag, N., Hendon, J. M., Hoffmayer, E. R., Kraus, R. T., McKinney, J. A., Secor, D. H., Stunz, G. W., Walter, J. F. 2019; 9
  • Population connectivity of pelagic megafauna in the Cuba-Mexico-United States triangle. Scientific reports Rooker, J. R., Dance, M. A., Wells, R. J., Ajemian, M. J., Block, B. A., Castleton, M. R., Drymon, J. M., Falterman, B. J., Franks, J. S., Hammerschlag, N., Hendon, J. M., Hoffmayer, E. R., Kraus, R. T., McKinney, J. A., Secor, D. H., Stunz, G. W., Walter, J. F. 2019; 9 (1): 1663

    Abstract

    The timing and extent of international crossings by billfishes, tunas, and sharks in the Cuba-Mexico-United States (U.S.) triangle was investigated using electronic tagging data from eight species that resulted in >22,000 tracking days. Transnational movements of these highly mobile marine predators were pronounced with varying levels of bi- or tri-national population connectivity displayed by each species. Billfishes and tunas moved throughout the Gulf of Mexico and all species investigated (blue marlin, white marlin, Atlantic bluefin tuna, yellowfin tuna) frequently crossed international boundaries and entered the territorial waters of Cuba and/or Mexico. Certain sharks (tiger shark, scalloped hammerhead) displayed prolonged periods of residency in U.S. waters with more limited displacements, while whale sharks and to a lesser degree shortfin mako moved through multiple jurisdictions. The spatial extent of associated movements was generally associated with their differential use of coastal and open ocean pelagic ecosystems. Species with the majority of daily positions in oceanic waters off the continental shelf showed the greatest tendency for transnational movements and typically traveled farther from initial tagging locations. Several species converged on a common seasonal movement pattern between territorial waters of the U.S. (summer) and Mexico (winter).

    View details for PubMedID 30733508

  • Temperature dependent pre- and postprandial activity in Pacific bluefin tuna (Thunnus orientalis). Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Gleiss, A. C., Dale, J. J., Klinger, D. H., Estess, E. E., Gardner, L. D., Machado, B., Norton, A. G., Farwell, C., Block, B. A. 2019

    Abstract

    Bluefin tunas are highly specialized fish with unique hydrodynamic designs and physiological traits. In this study, we present results in a captive population that demonstrate strong effects of ambient temperature on the tail beat frequency and swimming speed of a pelagic fish in both pre- and post-prandial states. We measured the responses of a ram ventilator, the Pacific bluefin tuna (Thunnus orientalis), after digestion of a meal to explore the impacts of the metabolic costs of digestion on behavior and respiration. A combination of respirometry, physiological biologging of visceral temperatures, and activity monitoring with accelerometry were used to explore the metabolic costs of digestion and the impacts on ventilation and swimming speed. Experiments were conducted at temperatures that are within the metabolic optimum for Pacific bluefin tuna (17 °C), and at a second temperature corresponding to the upper distributional limit of the species in the California Current (24 °C). Warmer temperatures resulted in higher tail-beat frequency and greater elevation of body temperature in pre-prandial Pacific bluefin tuna. Specific dynamic action (SDA) events resulted in a significant postprandial increase in tail-beat frequency of ~0.2 Hz, compared to pre-prandial levels of 1.5 Hz (17 °C) and 1.75 Hz (24 °C), possibly resulting from ventilator requirements. Data of fish exercised in a swim-tunnel respirometer suggest that the observed increase in tail-beat frequency comprise 5.5 and 6.8% of the oxygen demand during peak SDA at 24 °C and 17 °C respectively. The facultative increase in swimming speed might increase oxygen uptake at the gills to meet the increasing demand by visceral organs involved in the digestive process, potentially decreasing the available energy of each meal for other metabolic processes, such as growth, maturation, and reproduction. We hypothesize that these post-prandial behaviors allow tuna to evacuate their guts more quickly, ultimately permitting fish to feed more frequently when prey is available.

    View details for PubMedID 30735702

  • Global spatial risk assessment of sharks under the footprint of fisheries. Nature Queiroz, N., Humphries, N. E., Couto, A., Vedor, M., da Costa, I., Sequeira, A. M., Mucientes, G., Santos, A. M., Abascal, F. J., Abercrombie, D. L., Abrantes, K., Acuña-Marrero, D., Afonso, A. S., Afonso, P., Anders, D., Araujo, G., Arauz, R., Bach, P., Barnett, A., Bernal, D., Berumen, M. L., Lion, S. B., Bezerra, N. P., Blaison, A. V., Block, B. A., Bond, M. E., Bradford, R. W., Braun, C. D., Brooks, E. J., Brooks, A., Brown, J., Bruce, B. D., Byrne, M. E., Campana, S. E., Carlisle, A. B., Chapman, D. D., Chapple, T. K., Chisholm, J., Clarke, C. R., Clua, E. G., Cochran, J. E., Crochelet, E. C., Dagorn, L., Daly, R., Cortés, D. D., Doyle, T. K., Drew, M., Duffy, C. A., Erikson, T., Espinoza, E., Ferreira, L. C., Ferretti, F., Filmalter, J. D., Fischer, G. C., Fitzpatrick, R., Fontes, J., Forget, F., Fowler, M., Francis, M. P., Gallagher, A. J., Gennari, E., Goldsworthy, S. D., Gollock, M. J., Green, J. R., Gustafson, J. A., Guttridge, T. L., Guzman, H. M., Hammerschlag, N., Harman, L., Hazin, F. H., Heard, M., Hearn, A. R., Holdsworth, J. C., Holmes, B. J., Howey, L. A., Hoyos, M., Hueter, R. E., Hussey, N. E., Huveneers, C., Irion, D. T., Jacoby, D. M., Jewell, O. J., Johnson, R., Jordan, L. K., Jorgensen, S. J., Joyce, W., Daly, C. A., Ketchum, J. T., Klimley, A. P., Kock, A. A., Koen, P., Ladino, F., Lana, F. O., Lea, J. S., Llewellyn, F., Lyon, W. S., MacDonnell, A., Macena, B. C., Marshall, H., McAllister, J. D., McAuley, R., Meÿer, M. A., Morris, J. J., Nelson, E. R., Papastamatiou, Y. P., Patterson, T. A., Peñaherrera-Palma, C., Pepperell, J. G., Pierce, S. J., Poisson, F., Quintero, L. M., Richardson, A. J., Rogers, P. J., Rohner, C. A., Rowat, D. R., Samoilys, M., Semmens, J. M., Sheaves, M., Shillinger, G., Shivji, M., Singh, S., Skomal, G. B., Smale, M. J., Snyders, L. B., Soler, G., Soria, M., Stehfest, K. M., Stevens, J. D., Thorrold, S. R., Tolotti, M. T., Towner, A., Travassos, P., Tyminski, J. P., Vandeperre, F., Vaudo, J. J., Watanabe, Y. Y., Weber, S. B., Wetherbee, B. M., White, T. D., Williams, S., Zárate, P. M., Harcourt, R., Hays, G. C., Meekan, M. G., Thums, M., Irigoien, X., Eguiluz, V. M., Duarte, C. M., Sousa, L. L., Simpson, S. J., Southall, E. J., Sims, D. W. 2019

    Abstract

    Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively) and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of high-seas fishing effort. Results demonstrate an urgent need for conservation and management measures at high-seas shark hotspots and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real time, dynamic management.

    View details for DOI 10.1038/s41586-019-1444-4

    View details for PubMedID 31340216

  • Phylotranscriptomic insights into the diversification of endothermic Thunnus tunas. Molecular biology and evolution Ciezarek, A., Osborne, O., Shipley, O. N., Brooks, E. J., Tracey, S., McAllister, J., Gardner, L., Sternberg, M. J., Block, B., Savolainen, V. 2018

    Abstract

    Birds, mammals, and certain fishes, including tunas, opahs and lamnid sharks, are endothermic, conserving internally generated, metabolic heat to maintain body or tissue temperatures above that of the environment. Bluefin tunas are commercially important fishes worldwide and some populations are threatened. They are renowned for their endothermy, maintaining elevated temperatures of the oxidative locomotor muscle, viscera, brain and eyes, and occupying cold, productive high-latitude waters. Less cold-tolerant tunas, such as yellowfin tuna, by contrast, remain in warm-temperate to tropical waters year-round, reproducing more rapidly than most temperate bluefin tuna populations, providing resiliency in the face of large scale industrial fisheries. Despite the importance of these traits to not only fisheries, but responses to habitat utilisation and climate change, little is known of the genetic processes underlying the diversification of tunas. In collecting and analysing sequence data across 29,556 genes, we found that parallel selection on standing genetic variation is associated with the evolution of endothermy in bluefin tunas. This includes two shared substitutions in genes encoding glycerol-3 phosphate dehydrogenase, an enzyme that contributes to thermogenesis in bumblebees and mammals, as well as four genes involved in the Krebs cycle, oxidative phosphorylation, beta-oxidation and superoxide removal. Using phylogenetic techniques, we further illustrate that the eight Thunnus species are genetically distinct, but found evidence of mitochondrial genome introgression across two species. Phylogeny-based metrics highlight conservation needs for some of these species.

    View details for PubMedID 30364966

  • The political biogeography of migratory marine predators NATURE ECOLOGY & EVOLUTION Harrison, A., Costa, D. P., Winship, A. J., Benson, S. R., Bograd, S. J., Antolos, M., Carlisle, A. B., Dewar, H., Dutton, P. H., Jorgensen, S. J., Kohin, S., Mate, B. R., Robinson, P. W., Schaefer, K. M., Shaffer, S. A., Shillinger, G. L., Simmons, S. E., Weng, K. C., Gjerde, K. M., Block, B. A. 2018; 2 (10): 1571–78

    Abstract

    During their migrations, marine predators experience varying levels of protection and face many threats as they travel through multiple countries' jurisdictions and across ocean basins. Some populations are declining rapidly. Contributing to such declines is a failure of some international agreements to ensure effective cooperation by the stakeholders responsible for managing species throughout their ranges, including in the high seas, a global commons. Here we use biologging data from marine predators to provide quantitative measures with great potential to inform local, national and international management efforts in the Pacific Ocean. We synthesized a large tracking data set to show how the movements and migratory phenology of 1,648 individuals representing 14 species-from leatherback turtles to white sharks-relate to the geopolitical boundaries of the Pacific Ocean throughout species' annual cycles. Cumulatively, these species visited 86% of Pacific Ocean countries and some spent three-quarters of their annual cycles in the high seas. With our results, we offer answers to questions posed when designing international strategies for managing migratory species.

    View details for PubMedID 30177802

  • Response to Comment on "Tracking the global footprint of fisheries" SCIENCE Kroodsma, D. A., Mayorga, J., Hochberg, T., Miller, N. A., Boerder, K., Ferretti, F., Wilson, A., Bergman, B., White, T. D., Block, B. A., Woods, P., Sullivan, B., Costello, C., Worm, B. 2018; 361 (6404)

    Abstract

    Amoroso et al demonstrate the power of our data by estimating the high-resolution trawling footprint on seafloor habitat. Yet we argue that a coarser grid is required to understand full ecosystem impacts. Vessel tracking data allow us to estimate the footprint of human activities across a variety of scales, and the proper scale depends on the specific impact being investigated.

    View details for PubMedID 30139846

  • Shark baselines and the conservation role of remote coral reef ecosystems SCIENCE ADVANCES Ferretti, F., Curnick, D., Liu, K., Romanov, E. V., Block, B. A. 2018; 4 (3): eaaq0333

    Abstract

    Scientific monitoring has recorded only a recent fraction of the oceans' alteration history. This biases our understanding of marine ecosystems. Remote coral reef ecosystems are often considered pristine because of high shark abundance. However, given the long history and global nature of fishing, sharks' vulnerability, and the ecological consequences of shark declines, these states may not be natural. In the Chagos archipelago, one of the remotest coral reef systems on the planet, protected by a very large marine reserve, we integrated disparate fisheries and scientific survey data to reconstruct baselines and long-term population trajectories of two dominant sharks. In 2012, we estimated 571,310 gray reef and 31,693 silvertip sharks, about 79 and 7% of their baseline levels. These species were exploited longer and more intensively than previously thought and responded to fishing and protection with variable and compensatory population trajectories. Our approach highlights the value of integrative and historical analyses to evaluate large marine ecosystems currently considered pristine.

    View details for PubMedID 29532033

  • Tracking the global footprint of fisheries SCIENCE Kroodsma, D. A., Mayorga, J., Hochberg, T., Miller, N. A., Boerder, K., Ferretti, F., Wilson, A., Bergman, B., White, T. D., Block, B. A., Woods, P., Sullivan, B., Costello, C., Worm, B. 2018; 359 (6378): 904–7

    Abstract

    Although fishing is one of the most widespread activities by which humans harvest natural resources, its global footprint is poorly understood and has never been directly quantified. We processed 22 billion automatic identification system messages and tracked >70,000 industrial fishing vessels from 2012 to 2016, creating a global dynamic footprint of fishing effort with spatial and temporal resolution two to three orders of magnitude higher than for previous data sets. Our data show that industrial fishing occurs in >55% of ocean area and has a spatial extent more than four times that of agriculture. We find that global patterns of fishing have surprisingly low sensitivity to short-term economic and environmental variation and a strong response to cultural and political events such as holidays and closures.

    View details for PubMedID 29472481

  • Movements and dive behavior of juvenile California sea lions from Ano Nuevo Island MARINE MAMMAL SCIENCE McHuron, E. A., Block, B. A., Costa, D. P. 2018; 34 (1): 238–49

    View details for DOI 10.1111/mms.12449

    View details for Web of Science ID 000418337200016

  • Comparison of Mitochondrial Reactive Oxygen Species Production of Ectothermic and Endothermic Fish Muscle FRONTIERS IN PHYSIOLOGY Wiens, L., Banh, S., Sotiri, E., Jastroch, M., Block, B. A., Brand, M. D., Treberg, J. R. 2017; 8: 704

    Abstract

    Recently we demonstrated that the capacity of isolated muscle mitochondria to produce reactive oxygen species, measured as H2O2 efflux, is temperature-sensitive in isolated muscle mitochondria of ectothermic fish and the rat, a representative endothermic mammal. However, at physiological temperatures (15° and 37°C for the fish and rat, respectively), the fraction of total mitochondrial electron flux that generated H2O2, the fractional electron leak (FEL), was far lower in the rat than in fish. Those results suggested that the elevated body temperatures associated with endothermy may lead to a compensatory decrease in mitochondrial ROS production relative to respiratory capacity. To test this hypothesis we compare slow twitch (red) muscle mitochondria from the endothermic Pacific bluefin tuna (Thunnus orientalis) with mitochondria from three ectothermic fishes [rainbow trout (Oncorhynchus mykiss), common carp (Cyprinus carpio), and the lake sturgeon (Acipenser fulvescens)] and the rat. At a common assay temperature (25°C) rates of mitochondrial respiration and H2O2 efflux were similar in tuna and the other fishes. The thermal sensitivity of fish mitochondria was similar irrespective of ectothermy or endothermy. Comparing tuna to the rat at a common temperature, respiration rates were similar, or lower depending on mitochondrial substrates. FEL was not different across fish species at a common assay temperature (25°C) but was markedly higher in fishes than in rat. Overall, endothermy and warming of Pacific Bluefin tuna red muscle may increase the potential for ROS production by muscle mitochondria but the evolution of endothermy in this species is not necessarily associated with a compensatory reduction of ROS production relative to the respiratory capacity of mitochondria.

    View details for DOI 10.3389/fphys.2017.00704

    View details for Web of Science ID 000410763800001

    View details for PubMedID 28966595

    View details for PubMedCentralID PMC5605635

  • Oceanographic drivers of the vertical distribution of a highly migratory, endothermic shark SCIENTIFIC REPORTS Coffey, D. M., Carlisle, A. B., Hazen, E. L., Block, B. A. 2017; 7: 10434

    Abstract

    Salmon sharks Lamna ditropis are highly migratory, upper trophic level predators in North Pacific ecosystems. We analysed a multi-year satellite tag dataset to investigate the habitat use of female salmon sharks across their broad range in the eastern North Pacific (NEP) and identified key environmental factors that influence vertical distribution. Salmon sharks displayed remarkable plasticity in habitat use across disparate oceanographic regions in the NEP and increased utilization of deeper waters in offshore habitats. Diel shifts in vertical distribution and behaviour were consistently observed across their range and likely reflect shifts in their foraging ecology. Salmon sharks utilized a broad thermal niche and exhibited submergence behaviour, possibly for thermal refuge, when encountering sea surface temperatures outside their preferred temperature distribution. Moreover, the vertical distribution of salmon sharks indicates they were able to exploit low dissolved oxygen environments (<1-3 ml l-1), occasionally for extended periods of time in offshore habitats. However, salmon sharks generally reduced their use of deeper waters when encountering the combination of cold temperatures (<6 °C) and low dissolved oxygen concentrations (<1-3 ml l-1). Combining vertical distribution with high-resolution horizontal movements furthers our understanding of the ecological and environmental drivers of movement across short (diel) and long-term (migratory) scales.

    View details for PubMedID 28874881

  • Ocean Observations Using Tagged Animals OCEANOGRAPHY Roquet, F., Boehme, L., Block, B., Charrassin, J., Costa, D., Guinet, C., Harcourt, R. G., Hindell, M. A., Huckstadt, L. A., McMahon, C. R., Woodward, B., Fedak, M. A. 2017; 30 (2): 139
  • Biomonitoring of marine vertebrates in Monterey Bay using eDNA metabarcoding PLOS ONE Andruszkiewicz, E. A., Starks, H. A., Chavez, F. P., Sassoubre, L. M., Block, B. A., Boehm, A. B. 2017; 12 (4)

    Abstract

    Molecular analysis of environmental DNA (eDNA) can be used to assess vertebrate biodiversity in aquatic systems, but limited work has applied eDNA technologies to marine waters. Further, there is limited understanding of the spatial distribution of vertebrate eDNA in marine waters. Here, we use an eDNA metabarcoding approach to target and amplify a hypervariable region of the mitochondrial 12S rRNA gene to characterize vertebrate communities at 10 oceanographic stations spanning 45 km within the Monterey Bay National Marine Sanctuary (MBNMS). In this study, we collected three biological replicates of small volume water samples (1 L) at 2 depths at each of the 10 stations. We amplified fish mitochondrial DNA using a universal primer set. We obtained 5,644,299 high quality Illumina sequence reads from the environmental samples. The sequence reads were annotated to the lowest taxonomic assignment using a bioinformatics pipeline. The eDNA survey identified, to the lowest taxonomic rank, 7 families, 3 subfamilies, 10 genera, and 72 species of vertebrates at the study sites. These 92 distinct taxa come from 33 unique marine vertebrate families. We observed significantly different vertebrate community composition between sampling depths (0 m and 20/40 m deep) across all stations and significantly different communities at stations located on the continental shelf (<200 m bottom depth) versus in the deeper waters of the canyons of Monterey Bay (>200 m bottom depth). All but 1 family identified using eDNA metabarcoding is known to occur in MBNMS. The study informs the implementation of eDNA metabarcoding for vertebrate biomonitoring.

    View details for DOI 10.1371/journal.pone.0176343

    View details for Web of Science ID 000400308800048

    View details for PubMedID 28441466

  • Assessing the effectiveness of a large marine protected area for reef shark conservation BIOLOGICAL CONSERVATION White, T. D., Carlisle, A. B., Kroodsma, D. A., Block, B. A., Casagrandi, R., De Leo, G. A., Gatto, M., Michell, F., McCauley, D. J. 2017; 207: 64-71
  • Bioenergetics of captive yellowfin tuna (Thunnus albacares) AQUACULTURE Estess, E. E., Klinger, D. H., Coffey, D. M., Gleiss, A. C., Rowbotham, I., Seitz, A. C., Rodriguez, L., Norton, A., Block, B., Farwell, C. 2017; 468: 71-79
  • A Novel Cardiotoxic Mechanism for a Pervasive Global Pollutant SCIENTIFIC REPORTS Brette, F., Shiels, H. A., Galli, G. L., Cros, C., Incardona, J. P., Scholz, N. L., Block, B. A. 2017; 7

    Abstract

    The Deepwater Horizon disaster drew global attention to the toxicity of crude oil and the potential for adverse health effects amongst marine life and spill responders in the northern Gulf of Mexico. The blowout released complex mixtures of polycyclic aromatic hydrocarbons (PAHs) into critical pelagic spawning habitats for tunas, billfishes, and other ecologically important top predators. Crude oil disrupts cardiac function and has been associated with heart malformations in developing fish. However, the precise identity of cardiotoxic PAHs, and the mechanisms underlying contractile dysfunction are not known. Here we show that phenanthrene, a PAH with a benzene 3-ring structure, is the key moiety disrupting the physiology of heart muscle cells. Phenanthrene is a ubiquitous pollutant in water and air, and the cellular targets for this compound are highly conserved across vertebrates. Our findings therefore suggest that phenanthrene may be a major worldwide cause of vertebrate cardiac dysfunction.

    View details for DOI 10.1038/srep41476

    View details for Web of Science ID 000392958700001

    View details for PubMedID 28139666

    View details for PubMedCentralID PMC5282528

  • Influence of temperature and oxygen on the distribution of blue marlin (Makaira nigricans) in the Central Pacific FISHERIES OCEANOGRAPHY Carlisle, A. B., Kochevar, R. E., Arostegui, M. C., Ganong, J. E., Castleton, M., Schratwieser, J., Block, B. A. 2017; 26 (1): 34-48

    View details for DOI 10.1111/fog.12183

    View details for Web of Science ID 000389329300003

  • Hydraulic control of tuna fins: A role for the lymphatic system in vertebrate locomotion. Science (New York, N.Y.) Pavlov, V., Rosental, B., Hansen, N. F., Beers, J. M., Parish, G., Rowbotham, I., Block, B. A. 2017; 357 (6348): 310–14

    Abstract

    The lymphatic system in teleost fish has genetic and developmental origins similar to those of the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex, consisting of fin muscles, bones, and lymphatic vessels, is involved in the hydraulic control of median fins. This specialization of the lymphatic system is associated with fish in the family Scombridae and may have evolved in response to the demand for swimming and maneuvering control in these high-performance species.

    View details for PubMedID 28729512

  • A novel application of multi-event modeling to estimate class segregation in a highly migratory oceanic vertebrate ECOLOGY Chapple, T. K., Chambert, T., Kanive, P. E., Jorgensen, S. J., Rotella, J. J., Anderson, S. D., Carlisle, A. B., Block, B. A. 2016; 97 (12): 3494-3502

    Abstract

    Spatial segregation of animals by class (i.e., maturity or sex) within a population due to differential rates of temporary emigration (TE) from study sites can be an important life history feature to consider in population assessment and management. However, such rates are poorly known; new quantitative approaches to address these knowledge gaps are needed. We present a novel application of multi-event models that takes advantage of two sources of detections to differentiate temporary emigration from apparent absence to quantify class segregation within a study population of double-marked (photo-identified and tagged with coded acoustic transmitters) white sharks (Carcharodon carcharias) in central California. We use this model to test if sex-specific patterns in TE result in disparate apparent capture probabilities (p(o) ) between male and female white sharks, which can affect the observed sex ratio. The best-supported model showed a contrasting pattern of Pr(TE) from coastal aggregation sites between sexes (for males Pr[TE] = 0.015 [95% CI = 0.00, 0.31] and Pr[TE]= 0.57 [0.40, 0.72] for females), but not maturity classes. Additionally, by accounting for Pr(TE) and imperfect detection, we were able to estimate class-specific values of true capture probability (p(*) ) for tagged and untagged sharks. The best-supported model identified differences between maturity classes but no difference between sexes or tagging impacts (tagged mature sharks p(* ) = 0.55 (0.46-0.63) and sub-adult sharks p*( ) = 0.36 (0.25, 0.50); and untagged mature sharks p(* ) = 0.50 (0.39-0.61) and sub-adults p(* ) = 0.18 (0.10, 0.31). Estimated sex-based differences in p(o) were linked to sex-specific differences in Pr(TE) but not in p(*) ; once the Pr(TE) is accounted for, the p(*) between sexes was not different. These results indicate that the observed sex ratio is not a consequence of unequal detectability and sex-specific values of Pr(TE) are important drivers of the observed male-dominated sex ratio. Our modeling approach reveals complex class-specific patterns in Pr(TE) and p(*) in a mark-recapture data set, and highlights challenges for the population modeling and conservation of white sharks in central California. The model we develop here can be used to estimate rates of temporary emigration and class segregation when two detection methods are used.

    View details for DOI 10.1002/ecy.1589

    View details for Web of Science ID 000389444800026

    View details for PubMedID 27912002

  • Quantification of Environmental DNA (eDNA) Shedding and Decay Rates for Three Marine Fish ENVIRONMENTAL SCIENCE & TECHNOLOGY Sassoubre, L. M., Yamahara, K. M., Gardner, L. D., Block, B. A., Boehm, A. B. 2016; 50 (19): 10456-10464

    Abstract

    Analysis of environmental DNA (eDNA) to identify macroorganisms and biodiversity has the potential to significantly augment spatial and temporal biological monitoring in aquatic ecosystems. Current monitoring methods relying on the physical identification of organisms can be time consuming, expensive, and invasive. Measuring eDNA shed from organisms provides detailed information on the presence and abundance of communities of organisms. However, little is known about eDNA shedding and decay in aquatic environments. In the present study, we designed novel Taqman qPCR assays for three ecologically and economically important marine fish-Engraulis mordax (Northern Anchovy), Sardinops sagax (Pacific Sardine), and Scomber japonicas (Pacific Chub Mackerel). We subsequently measured fish eDNA shedding and decay rates in seawater mesocosms. eDNA shedding rates ranged from 165 to 3368 pg of DNA per hour per gram of biomass. First-order decay rate constants ranged from 0.055 to 0.101 per hour. We also examined the size fractionation of eDNA and concluded eDNA is both intra- and extracellular. Finally, we derived a simple mass-balance model to estimate fish abundance from eDNA concentration. The mesocosm-derived shedding and decay rates inform the interpretation of eDNA concentrations measured in environmental samples and future use of eDNA as a monitoring tool.

    View details for DOI 10.1021/acs.est.6b03114

    View details for Web of Science ID 000384841900019

    View details for PubMedID 27580258

  • Quantifying overlap between the Deepwater Horizon oil spill and predicted bluefin tuna spawning habitat in the Gulf of Mexico SCIENTIFIC REPORTS Hazen, E. L., Carlisle, A. B., Wilson, S. G., Ganong, J. E., Castleton, M. R., Schallert, R. J., Stokesbury, M. J., Bograd, S. J., Block, B. A. 2016; 6

    Abstract

    Atlantic bluefin tuna (Thunnus thynnus) are distributed throughout the North Atlantic and are both economically valuable and heavily exploited. The fishery is currently managed as two spawning populations, with the GOM population being severely depleted for over 20 years. In April-August of 2010, the Deepwater Horizon oil spill released approximately 4 million barrels of oil into the GOM, with severe ecosystem and economic impacts. Acute oil exposure results in mortality of bluefin eggs and larvae, while chronic effects on spawning adults are less well understood. Here we used 16 years of electronic tagging data for 66 bluefin tuna to identify spawning events, to quantify habitat preferences, and to predict habitat use and oil exposure within Gulf of Mexico spawning grounds. More than 54,000 km2 (5%) of predicted spawning habitat within the US EEZ was oiled during the week of peak oil dispersal, with potentially lethal effects on eggs and larvae. Although the oil spill overlapped with a relatively small portion of predicted spawning habitat, the cumulative impact from oil, ocean warming and bycatch mortality on GOM spawning grounds may result in significant effects for a population that shows little evidence of rebuilding.

    View details for DOI 10.1038/srep33824

    View details for Web of Science ID 000383692600001

    View details for PubMedCentralID PMC5031980

  • The effect of temperature on postprandial metabolism of yellowfin tuna (Thunnus albacares) COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY Klinger, D. H., Dale, J. J., Gleiss, A. C., Brandt, T., Estess, E. E., Gardner, L., Machado, B., Norton, A., Rodriguez, L., Stiltner, J., Farwell, C., Block, B. A. 2016; 195: 32-38

    Abstract

    Specific dynamic action (SDA), the increase in metabolic expenditure associated with consumption of a meal, represents a substantial portion of fish energy budgets and is highly influenced by ambient temperature. The effect of temperature on SDA has not been studied in yellowfin tuna (Thunnus albacares, Bonnaterre 1788), an active pelagic predator that occupies temperate and subtropical waters. The energetic cost and duration of SDA were calculated by comparing routine and post-prandial oxygen consumption rates. Mean routine metabolic rates in yellowfin tuna increased with temperature, from 136mgO2kg(-1)h(-1) at 20°C to 211mgO2kg(-1)h at 24°C. The mean duration of SDA decreased from 40.2h at 20°C to 33.1h at 24°C, while mean SDA coefficient, the percentage of energy in a meal that is consumed during digestion, increased from 5.9% at 20°C to 12.7% at 24°C. Digestion in yellowfin tuna is faster at a higher temperature but requires additional oxidative energy. Enhanced characterization of the role of temperature in SDA of yellowfin tuna deepens our understanding of tuna physiology and can help improve management of aquaculture and fisheries.

    View details for DOI 10.1016/j.cbpa.2016.01.005

    View details for Web of Science ID 000373410500005

    View details for PubMedID 26794613

  • Quantifying mercury isotope dynamics in captive Pacific bluefin tuna (Thunnus orientalis) ELEMENTA-SCIENCE OF THE ANTHROPOCENE Kwon, S., Blum, J. D., Madigan, D. J., Block, B. A., Popp, B. N. 2016; 4: 1–15
  • Quantifying overlap between the Deepwater Horizon oil spill and predicted bluefin tuna spawning habitat in the Gulf of Mexico. Scientific reports Hazen, E. L., Carlisle, A. B., Wilson, S. G., Ganong, J. E., Castleton, M. R., Schallert, R. J., Stokesbury, M. J., Bograd, S. J., Block, B. A. 2016; 6: 33824

    Abstract

    Atlantic bluefin tuna (Thunnus thynnus) are distributed throughout the North Atlantic and are both economically valuable and heavily exploited. The fishery is currently managed as two spawning populations, with the GOM population being severely depleted for over 20 years. In April-August of 2010, the Deepwater Horizon oil spill released approximately 4 million barrels of oil into the GOM, with severe ecosystem and economic impacts. Acute oil exposure results in mortality of bluefin eggs and larvae, while chronic effects on spawning adults are less well understood. Here we used 16 years of electronic tagging data for 66 bluefin tuna to identify spawning events, to quantify habitat preferences, and to predict habitat use and oil exposure within Gulf of Mexico spawning grounds. More than 54,000 km2 (5%) of predicted spawning habitat within the US EEZ was oiled during the week of peak oil dispersal, with potentially lethal effects on eggs and larvae. Although the oil spill overlapped with a relatively small portion of predicted spawning habitat, the cumulative impact from oil, ocean warming and bycatch mortality on GOM spawning grounds may result in significant effects for a population that shows little evidence of rebuilding.

    View details for PubMedID 27654709

  • Tracking the fidelity of Atlantic bluefin tuna released in Canadian waters to the Gulf of Mexico spawning grounds CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Wilson, S. G., Jonsen, I. D., Schallert, R. J., Ganong, J. E., Castleton, M. R., Spares, A. D., Boustany, A. M., Stokesbury, M. J., Block, B. A. 2015; 72 (11): 1700-1717
  • Life in the open ocean: seasonal migration and diel diving behaviour of Southern Hemisphere porbeagle sharks (Lamna nasus) MARINE BIOLOGY Francis, M. P., Holdsworth, J. C., Block, B. A. 2015; 162 (11): 2305–23
  • Exposure to Deepwater Horizon weathered crude oil increases routine metabolic demand in chub mackerel, Scomber japonicus. Marine pollution bulletin Klinger, D. H., Dale, J. J., Machado, B. E., Incardona, J. P., Farwell, C. J., Block, B. A. 2015; 98 (1-2): 259-266

    Abstract

    During the 2010 Deepwater Horizon incident, the continuous release of crude oil from the damaged Macondo 252 wellhead on the ocean floor contaminated surface water habitats for pelagic fish for more than 12weeks. The spill occurred across pelagic, neritic and benthic waters, impacting a variety of ecosystems. Chemical components of crude oil are known to disrupt cardiac function in juvenile fish, and here we investigate the effects of oil on the routine metabolic rate of chub mackerel, Scomber japonicus. Mackerel were exposed to artificially weathered Macondo 252 crude oil, prepared as a Water Accommodated Fraction (WAF), for 72 or 96h. Routine metabolic rates were determined pre- and post-exposure using an intermittent-flow, swim tunnel respirometer. Routine energetic demand increased in all mackerels in response to crude oil and reached statistical significance relative to unexposed controls at 96h. Chemical analyses of bile from exposed fish revealed elevated levels of fluorescent metabolites, confirming the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in the exposure WAF. The observed increase in metabolic demand is likely attributable to the bioenergetic costs of contaminant detoxification. These results indicate that short-term exposure (i.e. days) to oil has sub-lethal toxicity to mackerel and results in physiological stress during the active spill phase of the incident.

    View details for DOI 10.1016/j.marpolbul.2015.06.039

    View details for PubMedID 26210587

  • Direct quantification of energy intake in an apex marine predator suggests physiology is a key driver of migrations. Science advances Whitlock, R. E., Hazen, E. L., Walli, A., Farwell, C., Bograd, S. J., Foley, D. G., Castleton, M., Block, B. A. 2015; 1 (8)

    Abstract

    Pacific bluefin tuna (Thunnus orientalis) are highly migratory apex marine predators that inhabit a broad thermal niche. The energy needed for migration must be garnered by foraging, but measuring energy intake in the marine environment is challenging. We quantified the energy intake of Pacific bluefin tuna in the California Current using a laboratory-validated model, the first such measurement in a wild marine predator. Mean daily energy intake was highest off the coast of Baja California, Mexico in summer (mean ± SD, 1034 ± 669 kcal), followed by autumn when Pacific bluefin achieve their northernmost range in waters off northern California (944 ± 579 kcal). Movements were not always consistent with maximizing energy intake: the Pacific bluefin move out of energy rich waters both in late summer and winter, coincident with rising and falling water temperatures, respectively. We hypothesize that temperature-related physiological constraints drive migration and that Pacific bluefin tuna optimize energy intake within a range of optimal aerobic performance.

    View details for DOI 10.1126/sciadv.1400270

    View details for PubMedID 26601248

    View details for PubMedCentralID PMC4643779

  • Assessing niche width of endothermic fish from genes to ecosystem. Proceedings of the National Academy of Sciences of the United States of America Madigan, D. J., Carlisle, A. B., Gardner, L. D., Jayasundara, N., Micheli, F., Schaefer, K. M., Fuller, D. W., Block, B. A. 2015; 112 (27): 8350-8355

    Abstract

    Endothermy in vertebrates has been postulated to confer physiological and ecological advantages. In endothermic fish, niche expansion into cooler waters is correlated with specific physiological traits and is hypothesized to lead to greater foraging success and increased fitness. Using the seasonal co-occurrence of three tuna species in the eastern Pacific Ocean as a model system, we used cardiac gene expression data (as a proxy for thermal tolerance to low temperatures), archival tag data, and diet analyses to examine the vertical niche expansion hypothesis for endothermy in situ. Yellowfin, albacore, and Pacific bluefin tuna (PBFT) in the California Current system used more surface, mesopelagic, and deep waters, respectively. Expression of cardiac genes for calcium cycling increased in PBFT and coincided with broader vertical and thermal niche utilization. However, the PBFT diet was less diverse and focused on energy-rich forage fishes but did not show the greatest energy gains. Ecosystem-based management strategies for tunas should thus consider species-specific differences in physiology and foraging specialization.

    View details for DOI 10.1073/pnas.1500524112

    View details for PubMedID 26100889

    View details for PubMedCentralID PMC4500250

  • Mercury in Pacific bluefin tuna (Thunnus orientalis): bioaccumulation and trans-Pacific Ocean migration CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Colman, J. A., Nogueira, J. I., Pancorbo, O. C., Batdorf, C. A., Block, B. A. 2015; 72 (7): 1015-1023
  • Hearing thresholds of swimming Pacific bluefin tuna Thunnus orientalis JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY Dale, J. J., Gray, M. D., Popper, A. N., Rogers, P. H., Block, B. A. 2015; 201 (5): 441-454

    Abstract

    Pacific bluefin tuna (Thunnus orientalis) is a highly migratory, commercially valuable species potentially vulnerable to acoustic noise generated from human activities which could impact behavior and fitness. Although significant efforts have been made to understand hearing abilities of fishes, the large size and need to continuously swim for respiration have hindered investigations with tuna and other large pelagic species. In this study, Pacific bluefin tuna were trained to respond to a pure tone sound stimulus ranging 325-800 Hz and their hearing abilities quantified using a staircase psychophysical technique. Hearing was most sensitive from 400 to 500 Hz in terms of particle motion (radial acceleration -88 dB re 1 m s(-2); vertical acceleration -86 dB re 1 m s(-2)) and sound pressure (83 dB re 1 μPa). Compared to yellowfin tuna (Thunnus albacares) and kawakawa (Euthynnus affinis), Pacific bluefin tuna has a similar bandwidth of hearing and best frequency, but greater sensitivity overall. Careful calibration of the sound stimulus and experimental tank environment, as well as the adoption of behavioral methodology, demonstrates an experimental approach highly effective for the study of large fish species in the laboratory.

    View details for DOI 10.1007/s00359-015-0991-x

    View details for Web of Science ID 000353353700002

    View details for PubMedID 25732931

  • Reconstructing habitat use by juvenile salmon sharks links upwelling to strandings in the California Current MARINE ECOLOGY PROGRESS SERIES Carlisle, A. B., Litvin, S. Y., Hazen, E. L., Madigan, D. J., Goldman, K. J., Lea, R. N., Block, B. A. 2015; 525: 217-228

    View details for DOI 10.3354/meps11183

    View details for Web of Science ID 000354393700017

  • Effect of temperature acclimation on red blood cell oxygen affinity in Pacific bluefin tuna (Thunnus orientalis) and yellowfin tuna (Thunnus albacares) COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY Lilly, L. E., Bonaventura, J., Lipnick, M. S., Block, B. A. 2015; 181: 36-44

    Abstract

    Hemoglobin-oxygen (Hb-O2) binding properties are central to aerobic physiology, and must be optimized for an animal's aerobic requirements and environmental conditions, both of which can vary widely with seasonal changes or acutely with diving. In the case of tunas, the matter is further complicated by large regional temperature differences between tissues within the same animal. This study investigates the effects of thermal acclimation on red blood cell Hb-O2 binding in Pacific bluefin tuna (T. orientalis) and yellowfin tuna (T. albacares) maintained in captive tanks at acclimation temperatures of 17°, 20° and 24 °C. Oxygen binding properties of acclimated tuna isolated red blood cells were examined under varying experimental temperatures (15°-35 °C) and CO2 levels (0%, 0.5% and 1.5%). Results for Pacific bluefin tuna produced temperature-independence at 17 °C- and 20 °C-acclimation temperatures and significant reverse temperature-dependence at 24 °C-acclimation in the absence of CO2, with instances of reverse temperature-dependence in 17 °C- and 24 °C-acclimations at 0.5% and 1.5% CO2. In contrast, yellowfin tuna produced normal temperature-dependence at each acclimation temperature at 0% CO2, temperature-independence at 0.5% and 1.5% CO2, and significant reverse temperature-dependence at 17 °C-acclimation and 0.5% CO2. Thermal acclimation of Pacific bluefin tuna increased O2 binding affinity of the 17 °C-acclimation group, and produced a significantly steeper oxygen equilibrium curve slope (nH) at 24 °C-acclimation compared to the other acclimation temperatures. We discuss the potential implications of these findings below.

    View details for DOI 10.1016/j.cbpa.2014.11.014

    View details for Web of Science ID 000350081400005

    View details for PubMedID 25434601

  • Electronic Tagging of Atlantic Bluefin Tuna (Thunnus thynnus, L.) Reveals Habitat Use and Behaviors in the Mediterranean Sea PLOS ONE Cermeno, P., Quilez-Badia, G., Ospina-Alvarez, A., Sainz-Trapaga, S., Boustany, A. M., Seitz, A. C., Tudela, S., Block, B. A. 2015; 10 (2)

    Abstract

    We analyzed the movements of Atlantic tuna (Thunnus thynnus L.) in the Mediterranean Sea using data from 2 archival tags and 37 pop-up satellite archival tags (PAT). Bluefin tuna ranging in size from 12 to 248 kg were tagged on board recreational boats in the western Mediterranean and the Adriatic Sea between May and September during two different periods (2000 to 2001 and 2008 to 2012). Although tuna migrations between the Mediterranean Sea and the Atlantic Ocean have been well reported, our results indicate that part of the bluefin tuna population remains in the Mediterranean basin for much of the year, revealing a more complex population structure. In this study we demonstrate links between the western Mediterranean, the Adriatic and the Gulf of Sidra (Libya) using over 4336 recorded days of location and behavior data from tagged bluefin tuna with a maximum track length of 394 days. We described the oceanographic preferences and horizontal behaviors during the spawning season for 4 adult bluefin tuna. We also analyzed the time series data that reveals the vertical behavior of one pop-up satellite tag recovered, which was attached to a 43.9 kg tuna. This fish displayed a unique diving pattern within 16 days of the spawning season, suggesting a use of the thermocline as a thermoregulatory mechanism compatible with spawning. The results obtained hereby confirm that the Mediterranean is clearly an important habitat for this species, not only as spawning ground, but also as an overwintering foraging ground.

    View details for DOI 10.1371/journal.pone.0116638

    View details for Web of Science ID 000349545300022

    View details for PubMedID 25671316

    View details for PubMedCentralID PMC4324982

  • Stable isotope analysis of vertebrae reveals ontogenetic changes in habitat in an endothermic pelagic shark PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Carlisle, A. B., Goldman, K. J., Litvin, S. Y., Madigan, D. J., Bigman, J. S., Swithenbank, A. M., Kline, T. C., Block, B. A. 2015; 282 (1799)

    Abstract

    Ontogenetic changes in habitat are driven by shifting life-history requirements and play an important role in population dynamics. However, large portions of the life history of many pelagic species are still poorly understood or unknown. We used a novel combination of stable isotope analysis of vertebral annuli, Bayesian mixing models, isoscapes and electronic tag data to reconstruct ontogenetic patterns of habitat and resource use in a pelagic apex predator, the salmon shark (Lamna ditropis). Results identified the North Pacific Transition Zone as the major nursery area for salmon sharks and revealed an ontogenetic shift around the age of maturity from oceanic to increased use of neritic habitats. The nursery habitat may reflect trade-offs between prey availability, predation pressure and thermal constraints on juvenile endothermic sharks. The ontogenetic shift in habitat coincided with a reduction of isotopic niche, possibly reflecting specialization upon particular prey or habitats. Using tagging data to inform Bayesian isotopic mixing models revealed that adult sharks primarily use neritic habitats of Alaska yet receive a trophic subsidy from oceanic habitats. Integrating the multiple methods used here provides a powerful approach to retrospectively study the ecology and life history of migratory species throughout their ontogeny.

    View details for DOI 10.1098/rspb.2014.1446

    View details for Web of Science ID 000354866500003

    View details for PubMedID 25621332

    View details for PubMedCentralID PMC4286057

  • Bioenergetics of captive Pacific bluefin tuna (Thunnus orientalis) AQUACULTURE Estess, E. E., Coffey, D. M., Shimose, T., Seitz, A. C., Rodriguez, L., Norton, A., Block, B., Farwell, C. 2014; 434: 137-144
  • Reconstructing transoceanic migration patterns of Pacific bluefin tuna using a chemical tracer toolbox ECOLOGY Madigan, D. J., Baumann, Z., Carlisle, A. B., Hoen, D. K., Popp, B. N., Dewar, H., Snodgrass, O. E., Block, B. A., Fisher, N. S. 2014; 95 (6): 1674-1683

    Abstract

    Large pelagic predators play important roles in oceanic ecosystems, and may migrate vast distances to utilize resources in different marine ecoregions. Understanding movement patterns of migratory marine animals is critical for effective management, but often challenging, due to the cryptic habitat of pelagic migrators and the difficulty of assessing past movements. Chemical tracers can partially circumvent these challenges by reconstructing recent migration patterns. Pacific bluefin tuna (Thunnus orientalis; PBFT) inhabit the western and eastern Pacific Ocean, and are in steep decline due to overfishing. Understanding age-specific eastward transpacific migration patterns can improve management practices, but these migratory dynamics remain largely unquantified. Here, we combine a Fukushima-derived radiotracer (134Cs) with bulk tissue and amino acid stable isotope analyses of PBFT to distinguish recent migrants from residents of the eastern Pacific Ocean. The proportion of recent migrants to residents decreased in older year classes, though the proportion of older PBFT that recently migrated across the Pacific was greater than previous estimates. This novel toolbox of biogeochemical tracers can be applied to any species that crosses the North Pacific Ocean.

    View details for Web of Science ID 000337218500025

  • Deepwater Horizon crude oil impacts the developing hearts of large predatory pelagic fish PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Incardona, J. P., Gardner, L. D., Linbo, T. L., Brown, T. L., Esbaugh, A. J., Mager, E. M., Stieglitz, J. D., French, B. L., Labenia, J. S., Laetz, C. A., Tagal, M., Sloan, C. A., Elizur, A., Benetti, D. D., Grosell, M., Block, B. A., Scholz, N. L. 2014; 111 (15): E1510-E1518

    Abstract

    The Deepwater Horizon disaster released more than 636 million L of crude oil into the northern Gulf of Mexico. The spill oiled upper surface water spawning habitats for many commercially and ecologically important pelagic fish species. Consequently, the developing spawn (embryos and larvae) of tunas, swordfish, and other large predators were potentially exposed to crude oil-derived polycyclic aromatic hydrocarbons (PAHs). Fish embryos are generally very sensitive to PAH-induced cardiotoxicity, and adverse changes in heart physiology and morphology can cause both acute and delayed mortality. Cardiac function is particularly important for fast-swimming pelagic predators with high aerobic demand. Offspring for these species develop rapidly at relatively high temperatures, and their vulnerability to crude oil toxicity is unknown. We assessed the impacts of field-collected Deepwater Horizon (MC252) oil samples on embryos of three pelagic fish: bluefin tuna, yellowfin tuna, and an amberjack. We show that environmentally realistic exposures (1-15 µg/L total PAH) cause specific dose-dependent defects in cardiac function in all three species, with circulatory disruption culminating in pericardial edema and other secondary malformations. Each species displayed an irregular atrial arrhythmia following oil exposure, indicating a highly conserved response to oil toxicity. A considerable portion of Gulf water samples collected during the spill had PAH concentrations exceeding toxicity thresholds observed here, indicating the potential for losses of pelagic fish larvae. Vulnerability assessments in other ocean habitats, including the Arctic, should focus on the developing heart of resident fish species as an exceptionally sensitive and consistent indicator of crude oil impacts.

    View details for DOI 10.1073/pnas.1320950111

    View details for Web of Science ID 000334288600012

    View details for PubMedID 24706825

    View details for PubMedCentralID PMC3992643

  • Predicting bycatch hotspots for endangered leatherback turtles on longlines in the Pacific Ocean PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Roe, J. H., Morreale, S. J., Paladino, F. V., Shillinger, G. L., Benson, S. R., Eckert, S. A., Bailey, H., Santidrian Tomillo, P., Bograd, S. J., Eguchi, T., Dutton, P. H., Seminoff, J. A., Block, B. A., Spotila, J. R. 2014; 281 (1777)

    Abstract

    Fisheries bycatch is a critical source of mortality for rapidly declining populations of leatherback turtles, Dermochelys coriacea. We integrated use-intensity distributions for 135 satellite-tracked adult turtles with longline fishing effort to estimate predicted bycatch risk over space and time in the Pacific Ocean. Areas of predicted bycatch risk did not overlap for eastern and western Pacific nesting populations, warranting their consideration as distinct management units with respect to fisheries bycatch. For western Pacific nesting populations, we identified several areas of high risk in the north and central Pacific, but greatest risk was adjacent to primary nesting beaches in tropical seas of Indo-Pacific islands, largely confined to several exclusive economic zones under the jurisdiction of national authorities. For eastern Pacific nesting populations, we identified moderate risk associated with migrations to nesting beaches, but the greatest risk was in the South Pacific Gyre, a broad pelagic zone outside national waters where management is currently lacking and may prove difficult to implement. Efforts should focus on these predicted hotspots to develop more targeted management approaches to alleviate leatherback bycatch.

    View details for DOI 10.1098/rspb.2013.2559

    View details for Web of Science ID 000332382000013

    View details for PubMedID 24403331

    View details for PubMedCentralID PMC3896015

  • Crude Oil Impairs Cardiac Excitation-Contraction Coupling in Fish SCIENCE Brette, F., Machado, B., Cros, C., Incardona, J. P., Scholz, N. L., Block, B. A. 2014; 343 (6172): 772-776

    Abstract

    Crude oil is known to disrupt cardiac function in fish embryos. Large oil spills, such as the Deepwater Horizon (DWH) disaster that occurred in 2010 in the Gulf of Mexico, could severely affect fish at impacted spawning sites. The physiological mechanisms underlying such potential cardiotoxic effects remain unclear. Here, we show that crude oil samples collected from the DWH spill prolonged the action potential of isolated cardiomyocytes from juvenile bluefin and yellowfin tunas, through the blocking of the delayed rectifier potassium current (I(Kr)). Crude oil exposure also decreased calcium current (I(Ca)) and calcium cycling, which disrupted excitation-contraction coupling in cardiomyocytes. Our findings demonstrate a cardiotoxic mechanism by which crude oil affects the regulation of cellular excitability, with implications for life-threatening arrhythmias in vertebrates.

    View details for DOI 10.1126/science.1242747

    View details for Web of Science ID 000331557800040

    View details for PubMedID 24531969

  • Amino Acid Isotope Incorporation and Enrichment Factors in Pacific Bluefin Tuna, Thunnus orientalis PLOS ONE Bradley, C. J., Madigan, D. J., Block, B. A., Popp, B. N. 2014; 9 (1)

    Abstract

    Compound specific isotopic analysis (CSIA) of amino acids has received increasing attention in ecological studies in recent years due to its ability to evaluate trophic positions and elucidate baseline nutrient sources. However, the incorporation rates of individual amino acids into protein and specific trophic discrimination factors (TDFs) are largely unknown, limiting the application of CSIA to trophic studies. We determined nitrogen turnover rates of individual amino acids from a long-term (up to 1054 days) laboratory experiment using captive Pacific bluefin tuna, Thunnus orientalis (PBFT), a large endothermic pelagic fish fed a controlled diet. Small PBFT (white muscle δ(15)N∼11.5‰) were collected in San Diego, CA and transported to the Tuna Research and Conservation Center (TRCC) where they were fed a controlled diet with high δ(15)N values relative to PBFT white muscle (diet δ(15)N∼13.9‰). Half-lives of trophic and source amino acids ranged from 28.6 to 305.4 days and 67.5 to 136.2 days, respectively. The TDF for the weighted mean values of amino acids was 3.0 ‰, ranging from 2.2 to 15.8 ‰ for individual combinations of 6 trophic and 5 source amino acids. Changes in the δ(15)N values of amino acids across trophic levels are the underlying drivers of the trophic (15)N enrichment. Nearly all amino acid δ(15)N values in this experiment changed exponentially and could be described by a single compartment model. Significant differences in the rate of (15)N incorporation were found for source and trophic amino acids both within and between these groups. Varying half-lives of individual amino acids can be applied to migratory organisms as isotopic clocks, determining the length of time an individual has spent in a new environment. These results greatly enhance the ability to interpret compound specific isotope analyses in trophic studies.

    View details for DOI 10.1371/journal.pone.0085818

    View details for Web of Science ID 000330283100078

    View details for PubMedID 24465724

    View details for PubMedCentralID PMC3899081

  • Effects of temperature acclimation on Pacific bluefin tuna (Thunnus orientalis) cardiac transcriptome AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Jayasundara, N., Gardner, L. D., Block, B. A. 2013; 305 (9): R1010-R1020

    Abstract

    Little is known about the mechanisms underpinning thermal plasticity of vertebrate hearts. Bluefin tuna hearts offer a unique model to investigate processes underlying thermal acclimation. Their hearts, while supporting an endothermic physiology, operate at ambient temperature, and are presented with a thermal challenge when migrating to different thermal regimes. Here, we examined the molecular responses in atrial and ventricular tissues of Pacific bluefin tuna acclimated to 14°C, 20°C, and 25°C. Quantitative PCR studies showed an increase in sarcoplasmic reticulum Ca(2+) ATPase gene expression with cold acclimation and an induction of Na(+)/Ca(2+)-exchanger gene at both cold and warm temperatures. These data provide evidence for thermal plasticity of excitation-contraction coupling gene expression in bluefin tunas and indicate an increased capacity for internal Ca(2+) storage in cardiac myocytes at 14°C. Transcriptomic analysis showed profound changes in cardiac tissues with acclimation. A principal component analysis revealed that temperature effect was greatest on gene expression in warm-acclimated atrium. Overall data showed an increase in cardiac energy metabolism at 14°C, potentially compensating for cold temperature to optimize bluefin tuna performance in colder oceans. In contrast, metabolic enzyme activity and gene expression data suggest a decrease in ATP production at 25°C. Expression of genes involved in protein turnover and molecular chaperones was also decreased at 25°C. Expression of genes involved in oxidative stress response and programmed cell death suggest an increase in oxidative damage and apoptosis at 25°C, particularly in the atrium. These findings provide insights into molecular processes that may characterize cardiac phenotypes at upper thermal limits of teleosts.

    View details for DOI 10.1152/ajpregu.00254.2013

    View details for Web of Science ID 000326584200005

    View details for PubMedID 24005253

  • Quantifying energy intake in Pacific bluefin tuna (Thunnus orientalis) using the heat increment of feeding JOURNAL OF EXPERIMENTAL BIOLOGY Whitlock, R. E., Walli, A., Cermeno, P., Rodriguez, L. E., Farwell, C., Block, B. A. 2013; 216 (21): 4109-4123

    Abstract

    Using implanted archival tags, we examined the effects of meal caloric value, food type (sardine or squid) and ambient temperature on the magnitude and duration of the heat increment of feeding in three captive juvenile Pacific bluefin tuna. The objective of our study was to develop a model that can be used to estimate energy intake in wild fish of similar body mass. Both the magnitude and duration of the heat increment of feeding (measured by visceral warming) showed a strong positive correlation with the caloric value of the ingested meal. Controlling for meal caloric value, the extent of visceral warming was significantly greater at lower ambient temperature. The extent of visceral warming was also significantly higher for squid meals compared with sardine meals. By using a hierarchical Bayesian model to analyze our data and treating individuals as random effects, we demonstrate how increases in visceral temperature can be used to estimate the energy intake of wild Pacific bluefin tuna of similar body mass to the individuals used in our study.

    View details for DOI 10.1242/jeb.084335

    View details for Web of Science ID 000325806300027

    View details for PubMedID 24133153

  • Cumulative human impacts on marine predators. Nature communications Maxwell, S. M., Hazen, E. L., Bograd, S. J., Halpern, B. S., Breed, G. A., Nickel, B., Teutschel, N. M., Crowder, L. B., Benson, S., Dutton, P. H., Bailey, H., Kappes, M. A., Kuhn, C. E., Weise, M. J., Mate, B., Shaffer, S. A., Hassrick, J. L., Henry, R. W., Irvine, L., McDonald, B. I., Robinson, P. W., Block, B. A., Costa, D. P. 2013; 4: 2688-?

    Abstract

    Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n=685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.

    View details for DOI 10.1038/ncomms3688

    View details for PubMedID 24162104

  • Exxon Valdez to Deepwater Horizon: Comparable toxicity of both crude oils to fish early life stages AQUATIC TOXICOLOGY Incardona, J. P., Swarts, T. L., Edmunds, R. C., Linbo, T. L., Aquilina-Beck, A., Sloan, C. A., Gardner, L. D., Block, B. A., Scholz, N. L. 2013; 142: 303-316

    Abstract

    The 2010 Deepwater Horizon disaster in the Gulf of Mexico was the largest oil spill in United States history. Crude oils are highly toxic to developing fish embryos, and many pelagic fish species were spawning in the northern Gulf in the months before containment of the damaged Mississippi Canyon 252 (MC252) wellhead (April-July). The largest prior U.S. spill was the 1989 grounding of the Exxon Valdez that released 11 million gallons of Alaska North Slope crude oil (ANSCO) into Prince William Sound. Numerous studies in the aftermath of the Exxon Valdez spill defined a conventional crude oil injury phenotype in fish early life stages, mediated primarily by toxicity to the developing heart. To determine whether this type of injury extends to fishes exposed to crude oil from the Deepwater Horizon - MC252 incident, we used zebrafish to compare the embryotoxicity of ANSCO alongside unweathered and weathered MC252 oil. We also developed a standardized protocol for generating dispersed oil water-accommodated fractions containing microdroplets of crude oil in the size range of those detected in subsurface plumes in the Gulf. We show here that MC252 oil and ANSCO cause similar cardiotoxicity and photo-induced toxicity in zebrafish embryos. Morphological defects and patterns of cytochrome P450 induction were largely indistinguishable and generally correlated with polycyclic aromatic compound (PAC) composition of each oil type. Analyses of embryos exposed during different developmental windows provided additional insight into mechanisms of crude oil cardiotoxicity. These findings indicate that the impacts of MC252 crude oil on fish embryos and larvae are consistent with the canonical ANSCO cardiac injury phenotype. For those marine fish species that spawned in the northern Gulf of Mexico during and after the Deepwater Horizon incident, the established literature can therefore inform the assessment of natural resource injury in the form of potential year-class losses.

    View details for DOI 10.1016/j.aquatox.2013.08.011

    View details for Web of Science ID 000328093900031

  • Heart rate responses to temperature in free-swimming Pacific bluefin tuna (Thunnus orientalis) JOURNAL OF EXPERIMENTAL BIOLOGY Clark, T. D., Farwell, C. J., Rodriguez, L. E., Brandt, W. T., Block, B. A. 2013; 216 (17): 3208-3214

    Abstract

    The bluefin tuna heart remains at ambient water temperature (Ta) but must supply blood to warm regions of the body served by countercurrent vascular heat exchangers. Despite this unusual physiology, inherent difficulties have precluded an understanding of the cardiovascular responses to Ta in free-swimming bluefin tunas. We measured the heart rate (f(H)) responses of two captive Pacific bluefin tunas (Thunnus orientalis; 9.7 and 13.3 kg) over a cumulative period of 40 days. Routine f(H) during fasting in the holding tank at a Ta of 20°C was 45.1±8.0 and 40.7±6.5 beats min(-1) for Tuna 1 and Tuna 2, respectively. f(H) decreased in each fish with a Q10 temperature coefficient of 2.6 (Tuna 1) and 3.1 (Tuna 2) as Ta in the tank was slowly decreased to 15°C (~0.4°C h(-1)), despite a gradual increase in swimming speed. The same thermal challenge during digestion revealed similar thermal dependence of f(H) and indicated that the rate of visceral cooling is not buffered by the heat increment of feeding. Acutely decreasing Ta from 20 to 10°C while Tuna 1 swam in a tunnel respirometer caused a progressive increase in tail-beat frequency and oxygen consumption rate (M(O2)). f(H) of this fish decreased with a Q10 of 2.7 as Ta decreased between 20 and 15°C, while further cooling to 10°C saw a general plateau in f(H) around 35 beats min(-1) with a Q10 of 1.3. A discussion of the relationships between f(H), and haemoglobin-oxygen binding sheds further light on how bluefin cardiorespiratory systems function in a changing thermal environment.

    View details for DOI 10.1242/jeb.086546

    View details for Web of Science ID 000322955200014

    View details for PubMedID 23661777

  • Influence of Ambient Temperature on Specific Dynamic Action in Bluefin Tuna Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB) Gleiss, A. C., WHITLOCK, R. E., Dale, J. J., Clark, T. D., Block, B. A. OXFORD UNIV PRESS INC. 2013: E289–E289
  • Predicted habitat shifts of Pacific top predators in a changing climate NATURE CLIMATE CHANGE Hazen, E. L., Jorgensen, S., Rykaczewski, R. R., Bograd, S. J., Foley, D. G., Jonsen, I. D., Shaffer, S. A., Dunne, J. P., Costa, D. P., Crowder, L. B., Block, B. A. 2013; 3 (3): 234-238
  • Archival and acoustic tags reveal the post-spawning migrations, diving behavior, and thermal habitat of hatchery-origin Sacramento River steelhead kelts (Oncorhynchus mykiss) ENVIRONMENTAL BIOLOGY OF FISHES Teo, S. L., Sandstrom, P. T., Chapman, E. D., Null, R. E., Brown, K., Klimley, A. P., Block, B. A. 2013; 96 (2-3): 175-187
  • Travelling light: white sharks (Carcharodon carcharias) rely on body lipid stores to power ocean-basin scale migration. Proceedings. Biological sciences / The Royal Society Del Raye, G., Jorgensen, S. J., Krumhansl, K., Ezcurra, J. M., Block, B. A. 2013; 280 (1766): 20130836-?

    Abstract

    Many species undertake long-distance annual migrations between foraging and reproductive areas. Such migrants depend on the efficient packaging, storage and utilization of energy to succeed. A diverse assemblage of organisms accomplishes this through the use of lipid reserves; yet, it remains unclear whether the migrations of elasmobranchs, which include the largest gill breathers on Earth, depend on such a mechanism. We examine depth records from pop-up satellite archival tags to discern changes in buoyancy as a proxy for energy storage in Eastern Pacific white sharks, and assess whether lipid depletion fuels long-distance (approx. 4000 km) migrations. We develop new algorithms to assess body condition, buoyancy and drift rate during drift dives and validate the techniques using a captive white shark. In the wild, we document a consistent increase in drift rate over the course of all migrations, indicating a decrease in buoyancy caused by the depletion of lipid reserves. These results comprise, to our knowledge, the first assessment of energy storage and budgeting in migrating sharks. The methods provide a basis for further insights into using electronic tags to reveal the energetic strategies of a wide range of elasmobranchs.

    View details for DOI 10.1098/rspb.2013.0836

    View details for PubMedID 23864595

  • Cumulative human impacts on marine predators. Nature communications Maxwell, S. M., Hazen, E. L., Bograd, S. J., Halpern, B. S., Breed, G. A., Nickel, B., Teutschel, N. M., Crowder, L. B., Benson, S., Dutton, P. H., Bailey, H., Kappes, M. A., Kuhn, C. E., Weise, M. J., Mate, B., Shaffer, S. A., Hassrick, J. L., Henry, R. W., Irvine, L., McDonald, B. I., Robinson, P. W., Block, B. A., Costa, D. P. 2013; 4: 2688-?

    Abstract

    Stressors associated with human activities interact in complex ways to affect marine ecosystems, yet we lack spatially explicit assessments of cumulative impacts on ecologically and economically key components such as marine predators. Here we develop a metric of cumulative utilization and impact (CUI) on marine predators by combining electronic tracking data of eight protected predator species (n=685 individuals) in the California Current Ecosystem with data on 24 anthropogenic stressors. We show significant variation in CUI with some of the highest impacts within US National Marine Sanctuaries. High variation in underlying species and cumulative impact distributions means that neither alone is sufficient for effective spatial management. Instead, comprehensive management approaches accounting for both cumulative human impacts and trade-offs among multiple stressors must be applied in planning the use of marine resources.

    View details for DOI 10.1038/ncomms3688

    View details for PubMedID 24162104

  • Eating or Meeting? Cluster Analysis Reveals Intricacies of White Shark (Carcharodon carcharias) Migration and Offshore Behavior PLOS ONE Jorgensen, S. J., Arnoldi, N. S., Estess, E. E., Chapple, T. K., Rueckert, M., Anderson, S. D., Block, B. A. 2012; 7 (10)

    Abstract

    Elucidating how mobile ocean predators utilize the pelagic environment is vital to understanding the dynamics of oceanic species and ecosystems. Pop-up archival transmitting (PAT) tags have emerged as an important tool to describe animal migrations in oceanic environments where direct observation is not feasible. Available PAT tag data, however, are for the most part limited to geographic position, swimming depth and environmental temperature, making effective behavioral observation challenging. However, novel analysis approaches have the potential to extend the interpretive power of these limited observations. Here we developed an approach based on clustering analysis of PAT daily time-at-depth histogram records to distinguish behavioral modes in white sharks (Carcharodon carcharias). We found four dominant and distinctive behavioral clusters matching previously described behavioral patterns, including two distinctive offshore diving modes. Once validated, we mapped behavior mode occurrence in space and time. Our results demonstrate spatial, temporal and sex-based structure in the diving behavior of white sharks in the northeastern Pacific previously unrecognized including behavioral and migratory patterns resembling those of species with lek mating systems. We discuss our findings, in combination with available life history and environmental data, and propose specific testable hypotheses to distinguish between mating and foraging in northeastern Pacific white sharks that can provide a framework for future work. Our methodology can be applied to similar datasets from other species to further define behaviors during unobservable phases.

    View details for DOI 10.1371/journal.pone.0047819

    View details for Web of Science ID 000310705300018

    View details for PubMedID 23144707

    View details for PubMedCentralID PMC3483152

  • Microarray gene expression profiles from mature gonad tissues of Atlantic bluefin tuna, Thunnus thynnus in the Gulf of Mexico BMC GENOMICS Gardner, L. D., Jayasundara, N., Castilho, P. C., Block, B. 2012; 13

    Abstract

    Bluefin tunas are highly prized pelagic fish species representing a significant economic resource to fisheries throughout the world. Atlantic bluefin tuna (Thunnus thynnus) populations have significantly declined due to overexploitation. As a consequence of their value and population decline, T. thynnus has been the focus of considerable research effort concerning many aspects of their life history. However, in-depth understanding of T. thynnus reproductive biology is still lacking. Knowledge of reproductive physiology is a very important tool for determining effective fisheries and aquaculture management. Transcriptome techniques are proving powerful and provide novel insights into physiological processes. Construction of a microarray from T. thynnus ESTs sourced from reproductive tissues has provided an ideal platform to study the reproductive physiology of bluefin tunas. The aim of this investigation was to compare transcription profiles from the ovaries and testes of mature T. thynnus to establish sex specific variations underlying their reproductive physiology.Male and females T. thynnus gonad tissues were collected from the wild and histologically staged. Sub-samples of sexually mature tissues were also measured for their mRNA differential expression among the sexes using the custom microarray design BFT 4X44K. A total of 7068 ESTs were assessed for differential expression of which 1273 ESTs were significantly different (p<0.05) with >2 fold change in expression according to sex. Differential expression for 13 of these ESTs was validated with quantitative PCR. These include genes involved in egg envelope formation, hydration, and lipid transport/accumulation more highly expressed in ovaries compared with testis, while genes involved in meiosis, sperm motility and lipid metabolism were more highly expressed in testis compared with ovaries.This investigation has furthered our knowledge of bluefin tunas reproductive biology by using a contemporary transcriptome approach. Gene expression profiles in T. thynnus sexually mature testes and ovaries were characterized with reference to gametogenesis and potential alternative functions. This report is the first application of microarray technology for bluefin tunas and demonstrates the efficacy by which this technique may be used for further characterization of specific biological aspects for this valuable teleost fish.

    View details for DOI 10.1186/1471-2164-13-530

    View details for Web of Science ID 000310085500001

    View details for PubMedID 23036107

    View details for PubMedCentralID PMC3478158

  • Stable Isotope Analysis Challenges Wasp-Waist Food Web Assumptions in an Upwelling Pelagic Ecosystem SCIENTIFIC REPORTS Madigan, D. J., Carlisle, A. B., Dewar, H., Snodgrass, O. E., Litvin, S. Y., Micheli, F., Block, B. A. 2012; 2

    Abstract

    Eastern boundary currents are often described as 'wasp-waist' ecosystems in which one or few mid-level forage species support a high diversity of larger predators that are highly susceptible to fluctuations in prey biomass. The assumption of wasp-waist control has not been empirically tested in all such ecosystems. This study used stable isotope analysis to test the hypothesis of wasp-waist control in the southern California Current large marine ecosystem (CCLME). We analyzed prey and predator tissue for δ¹³C and δ¹⁵N and used Bayesian mixing models to provide estimates of CCLME trophic dynamics from 2007-2010. Our results show high omnivory, planktivory by some predators, and a higher degree of trophic connectivity than that suggested by the wasp-waist model. Based on this study period, wasp-waist models oversimplify trophic dynamics within the CCLME and potentially other upwelling, pelagic ecosystems. Higher trophic connectivity in the CCLME likely increases ecosystem stability and resilience to perturbations.

    View details for DOI 10.1038/srep00654

    View details for Web of Science ID 000308807000002

    View details for PubMedID 22977729

    View details for PubMedCentralID PMC3440624

  • Movement Patterns for a Critically Endangered Species, the Leatherback Turtle (Dermochelys coriacea), Linked to Foraging Success and Population Status PLOS ONE Bailey, H., Fossette, S., Bograd, S. J., Shillinger, G. L., Swithenbank, A. M., Georges, J., Gaspar, P., Stromberg, K. H., Paladino, F. V., Spotila, J. R., Block, B. A., Hays, G. C. 2012; 7 (5)

    Abstract

    Foraging success for pelagic vertebrates may be revealed by horizontal and vertical movement patterns. We show markedly different patterns for leatherback turtles in the North Atlantic versus Eastern Pacific, which feed on gelatinous zooplankton that are only occasionally found in high densities. In the Atlantic, travel speed was characterized by two modes, indicative of high foraging success at low speeds (<15 km d(-1)) and transit at high speeds (20-45 km d(-1)). Only a single mode was evident in the Pacific, which occurred at speeds of 21 km d(-1) indicative of transit. The mean dive depth was more variable in relation to latitude but closer to the mean annual depth of the thermocline and nutricline for North Atlantic than Eastern Pacific turtles. The most parsimonious explanation for these findings is that Eastern Pacific turtles rarely achieve high foraging success. This is the first support for foraging behaviour differences between populations of this critically endangered species and suggests that longer periods searching for prey may be hindering population recovery in the Pacific while aiding population maintenance in the Atlantic.

    View details for DOI 10.1371/journal.pone.0036401

    View details for Web of Science ID 000305341300016

    View details for PubMedID 22615767

    View details for PubMedCentralID PMC3354004

  • Estimating fishing and natural mortality rates for Pacific bluefin tuna (Thunnus orientalis) using electronic tagging data FISHERIES RESEARCH Whitlock, R. E., McAllister, M. K., Block, B. A. 2012; 119: 115-127
  • Warm fish with cold hearts: Cardiac thermal plasticity of Pacific bluefin tuna Thunnus orientalis Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB)/Symposium on New Frontiers from Marine Snakes to Marine Ecosystems Jayasundara, N., Gardner, L. D., Towle, D. T., Block, B. A. OXFORD UNIV PRESS INC. 2012: E86–E86
  • Identification of distinct movement patterns in Pacific leatherback turtle populations influenced by ocean conditions ECOLOGICAL APPLICATIONS Bailey, H., Benson, S. R., Shillinger, G. L., Bograd, S. J., Dutton, P. H., Eckert, S. A., Morreale, S. J., Paladino, F. V., Eguchi, T., Foley, D. G., Block, B. A., Piedra, R., Hitipeuw, C., Tapilatu, R. F., Spotila, J. R. 2012; 22 (3): 735-747

    Abstract

    Interactions with fisheries are believed to be a major cause of mortality for adult leatherback turtles (Dermochelys coriacea), which is of particular concern in the Pacific Ocean, where they have been rapidly declining. In order to identify where these interactions are occurring and how they may be reduced, it is essential first to understand the movements and behavior of leatherback turtles. There are two regional nesting populations in the East Pacific (EP) and West Pacific (WP), comprising multiple nesting sites. We synthesized tracking data from the two populations and compared their movement patterns. A switching state-space model was applied to 135 Argos satellite tracks to account for observation error, and to distinguish between migratory and area-restricted search behaviors. The tracking data, from the largest leatherback data set ever assembled, indicated that there was a high degree of spatial segregation between EP and WP leatherbacks. Area-restricted search behavior mainly occurred in the southeast Pacific for the EP leatherbacks, whereas the WP leatherbacks had several different search areas in the California Current, central North Pacific, South China Sea, off eastern Indonesia, and off southeastern Australia. We also extracted remotely sensed oceanographic data and applied a generalized linear mixed model to determine if leatherbacks exhibited different behavior in relation to environmental variables. For the WP population, the probability of area-restricted search behavior was positively correlated with chlorophyll-a concentration. This response was less strong in the EP population, but these turtles had a higher probability of search behavior where there was greater Ekman upwelling, which may increase the transport of nutrients and consequently prey availability. These divergent responses to oceanographic conditions have implications for leatherback vulnerability to fisheries interactions and to the effects of climate change. The occurrence of leatherback turtles within both coastal and pelagic areas means they have a high risk of exposure to many different fisheries, which may be very distant from their nesting sites. The EP leatherbacks have more limited foraging grounds than the WP leatherbacks, which could make them more susceptible to any temperature or prey changes that occur in response to climate change.

    View details for Web of Science ID 000303312000001

    View details for PubMedID 22645807

  • State-space framework for estimating measurement error from double-tagging telemetry experiments METHODS IN ECOLOGY AND EVOLUTION Winship, A. J., Jorgensen, S. J., Shaffer, S. A., Jonsen, I. D., Robinson, P. W., Costa, D. P., Block, B. A. 2012; 3 (2): 291-302
  • Thermal dependence of cardiac SR Ca2+-ATPase from fish and mammals JOURNAL OF THERMAL BIOLOGY Landeira-Fernandez, A. M., Castilho, P. C., Block, B. A. 2012; 37 (3): 217-223
  • Using Stable Isotope Analysis to Understand the Migration and Trophic Ecology of Northeastern Pacific White Sharks (Carcharodon carcharias) PLOS ONE Carlisle, A. B., Kim, S. L., Semmens, B. X., Madigan, D. J., Jorgensen, S. J., Perle, C. R., Anderson, S. D., Chapple, T. K., Kanive, P. E., Block, B. A. 2012; 7 (2)

    Abstract

    The white shark (Carcharodon carcharias) is a wide-ranging apex predator in the northeastern Pacific (NEP). Electronic tagging has demonstrated that white sharks exhibit a regular migratory pattern, occurring at coastal sites during the late summer, autumn and early winter and moving offshore to oceanic habitats during the remainder of the year, although the purpose of these migrations remains unclear. The purpose of this study was to use stable isotope analysis (SIA) to provide insight into the trophic ecology and migratory behaviors of white sharks in the NEP. Between 2006 and 2009, 53 white sharks were biopsied in central California to obtain dermal and muscle tissues, which were analyzed for stable isotope values of carbon (δ(13)C) and nitrogen (δ(15)N). We developed a mixing model that directly incorporates movement data and tissue incorporation (turnover) rates to better estimate the relative importance of different focal areas to white shark diet and elucidate their migratory behavior. Mixing model results for muscle showed a relatively equal dietary contribution from coastal and offshore regions, indicating that white sharks forage in both areas. However, model results indicated that sharks foraged at a higher relative rate in coastal habitats. There was a negative relationship between shark length and muscle δ(13)C and δ(15)N values, which may indicate ontogenetic changes in habitat use related to onset of maturity. The isotopic composition of dermal tissue was consistent with a more rapid incorporation rate than muscle and may represent more recent foraging. Low offshore consumption rates suggest that it is unlikely that foraging is the primary purpose of the offshore migrations. These results demonstrate how SIA can provide insight into the trophic ecology and migratory behavior of marine predators, especially when coupled with electronic tagging data.

    View details for DOI 10.1371/journal.pone.0030492

    View details for Web of Science ID 000302741300013

    View details for PubMedID 22355313

    View details for PubMedCentralID PMC3280240

  • Atlantic Bluefin Tuna: A Novel Multistock Spatial Model for Assessing Population Biomass PLOS ONE Taylor, N. G., McAllister, M. K., Lawson, G. L., Carruthers, T., Block, B. A. 2011; 6 (12): e27693

    Abstract

    Atlantic bluefin tuna (Thunnus thynnus) is considered to be overfished, but the status of its populations has been debated, partly because of uncertainties regarding the effects of mixing on fishing grounds. A better understanding of spatial structure and mixing may help fisheries managers to successfully rebuild populations to sustainable levels while maximizing catches. We formulate a new seasonally and spatially explicit fisheries model that is fitted to conventional and electronic tag data, historic catch-at-age reconstructions, and otolith microchemistry stock-composition data to improve the capacity to assess past, current, and future population sizes of Atlantic bluefin tuna. We apply the model to estimate spatial and temporal mixing of the eastern (Mediterranean) and western (Gulf of Mexico) populations, and to reconstruct abundances from 1950 to 2008. We show that western and eastern populations have been reduced to 17% and 33%, respectively, of 1950 spawning stock biomass levels. Overfishing to below the biomass that produces maximum sustainable yield occurred in the 1960s and the late 1990s for western and eastern populations, respectively. The model predicts that mixing depends on season, ontogeny, and location, and is highest in the western Atlantic. Assuming that future catches are zero, western and eastern populations are predicted to recover to levels at maximum sustainable yield by 2025 and 2015, respectively. However, the western population will not recover with catches of 1750 and 12,900 tonnes (the "rebuilding quotas") in the western and eastern Atlantic, respectively, with or without closures in the Gulf of Mexico. If future catches are double the rebuilding quotas, then rebuilding of both populations will be compromised. If fishing were to continue in the eastern Atlantic at the unregulated levels of 2007, both stocks would continue to decline. Since populations mix on North Atlantic foraging grounds, successful rebuilding policies will benefit from trans-Atlantic cooperation.

    View details for DOI 10.1371/journal.pone.0027693

    View details for Web of Science ID 000298365700007

    View details for PubMedID 22174745

    View details for PubMedCentralID PMC3235089

  • Movements, behavior, and habitat utilization of yellowfin tuna (Thunnus albacares) in the Pacific Ocean off Baja California, Mexico, determined from archival tag data analyses, including unscented Kalman filtering FISHERIES RESEARCH Schaefer, K. M., Fuller, D. W., Block, B. A. 2011; 112 (1-2): 22-37
  • Seasonal changes in depth distribution of salmon sharks (Lamna ditropis) in Alaskan waters: implications for foraging ecology CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Carlisle, A. B., Perle, C. R., Goldman, K. J., Block, B. A. 2011; 68 (11): 1905-1921

    View details for DOI 10.1139/F2011-105

    View details for Web of Science ID 000298441500004

  • The role of discounting and dynamics in determining the economic efficiency of time-area closures for managing fishery bycatch THEORETICAL ECOLOGY Armsworth, P. R., Block, B. A., Eagle, J., Roughgarden, J. E. 2011; 4 (4): 513-526
  • Temperature dependence of cardiac sarcoplasmic reticulum Ca2+-ATPase from rainbow trout Oncorhynchus mykiss JOURNAL OF FISH BIOLOGY Da Silva, D., Costa, D. C., Alves, C. M., Block, B. A., Landeira-Fernandez, A. M. 2011; 79 (3): 789-800

    Abstract

    In this work, the temperature dependence of the sarco-endoplasmic reticulum Ca(2+) -ATPase (SERCA2) activity from rainbow trout Oncorhynchus mykiss cardiac ventricles was measured and compared with the mammalian SERCA2 isoform. The rate of ATP-dependent Ca(2+) transport catalysed by O. mykiss vesicles was totally abolished by thapsigargin and the Ca(2+) ionophore A(23187) . At warm temperatures (25 and 30° C), the SERCA2 from O. mykiss ventricles displayed the same rate of Ca(2+) uptake. At 35° C, the activity of the O. mykiss enzyme decreased after 20 min of reaction time. The rate of Ca(2+) uptake catalysed by the mammalian SERCA2 was temperature dependent exhibiting its maximal activity at 35° C. In contrast to the rate of Ca(2+) uptake, the rate of ATP hydrolysis catalysed by O. mykiss SERCA2 was not significantly different at 25 and 35° C, but the rate of ATP hydrolysis catalysed by the rat Rattus norvegicus SERCA2 isoform at 35° C was two-fold higher than at 25° C. At low temperatures (5 to 20° C), the rate of Ca(2+) uptake from O. mykiss SR was less temperature dependent than the R. norvegicus isoform, being able to sustain a high activity even at 5° C. The mean ±s.e. Q(10) values calculated from 25 to 35° C for ATP hydrolysis were 1·112 ± 0·026 (n = 3) and 2·759 ± 0·240 (n = 5) for O. mykiss and R. norvegicus, respectively. Taken together, the results show that the O. mykiss SERCA2 was not temperature dependent over the 10 to 25° C temperature interval commonly experienced by the animal in vivo. The Q(10) value of SERCA2 was significantly lower in O. mykiss than R. norvegicus which may be key for cardiac function over the wide environmental temperatures experienced in this eurythermal fish.

    View details for DOI 10.1111/j.1095-8649.2011.03076.x

    View details for Web of Science ID 000294598300014

    View details for PubMedID 21884113

  • A first estimate of white shark, Carcharodon carcharias, abundance off Central California BIOLOGY LETTERS Chapple, T. K., Jorgensen, S. J., Anderson, S. D., Kanive, P. E., Klimley, A. P., Botsford, L. W., Block, B. A. 2011; 7 (4): 581-583

    Abstract

    The decline of sharks in the global oceans underscores the need for careful assessment and monitoring of remaining populations. The northeastern Pacific is the home range for a genetically distinct clade of white sharks (Carcharodon carcharias). Little is known about the conservation status of this demographically isolated population, concentrated seasonally at two discrete aggregation sites: Central California (CCA) and Guadalupe Island, Mexico. We used photo-identification of dorsal fins in a sequential Bayesian mark-recapture algorithm to estimate white shark abundance off CCA. We collected 321 photographs identifying 130 unique individuals, and estimated the abundance off CCA to be 219 mature and sub-adult individuals ((130, 275) 95% credible intervals), substantially smaller than populations of other large marine predators. Our methods can be readily expanded to estimate shark population abundance at other locations, and over time, to monitor the status, population trends and protection needs of these globally distributed predators.

    View details for DOI 10.1098/rsbl.2011.0124

    View details for Web of Science ID 000292639100030

    View details for PubMedID 21389017

    View details for PubMedCentralID PMC3130246

  • Tracking apex marine predator movements in a dynamic ocean NATURE Block, B. A., Jonsen, I. D., Jorgensen, S. J., Winship, A. J., Shaffer, S. A., Bograd, S. J., Hazen, E. L., Foley, D. G., Breed, G. A., Harrison, A., Ganong, J. E., Swithenbank, A., Castleton, M., Dewar, H., Mate, B. R., SHILLINGER, G. L., Schaefer, K. M., Benson, S. R., Weise, M. J., Henry, R. W., Costa, D. P. 2011; 475 (7354): 86-90

    Abstract

    Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.

    View details for DOI 10.1038/nature10082

    View details for PubMedID 21697831

  • Long-term individual identification and site fidelity of white sharks, Carcharodon carcharias, off California using dorsal fins MARINE BIOLOGY Anderson, S. D., Chapple, T. K., Jorgensen, S. J., Klimley, A. P., Block, B. A. 2011; 158 (6): 1233-1237
  • Convergent evolution in locomotory patterns of flying and swimming animals NATURE COMMUNICATIONS Gleiss, A. C., Jorgensen, S. J., Liebsch, N., Sala, J. E., Norman, B., Hays, G. C., Quintana, F., Grundy, E., Campagna, C., Trites, A. W., Block, B. A., Wilson, R. P. 2011; 2

    Abstract

    Locomotion is one of the major energetic costs faced by animals and various strategies have evolved to reduce its cost. Birds use interspersed periods of flapping and gliding to reduce the mechanical requirements of level flight while undergoing cyclical changes in flight altitude, known as undulating flight. Here we equipped free-ranging marine vertebrates with accelerometers and demonstrate that gait patterns resembling undulating flight occur in four marine vertebrate species comprising sharks and pinnipeds. Both sharks and pinnipeds display intermittent gliding interspersed with powered locomotion. We suggest, that the convergent use of similar gait patterns by distinct groups of animals points to universal physical and physiological principles that operate beyond taxonomic limits and shape common solutions to increase energetic efficiency. Energetically expensive large-scale migrations performed by many vertebrates provide common selection pressure for efficient locomotion, with potential for the convergence of locomotory strategies by a wide variety of species.

    View details for DOI 10.1038/ncomms1350

    View details for Web of Science ID 000294804400018

    View details for PubMedID 21673673

  • Temperature effects on Ca2+ cycling in scombrid cardiomyocytes: a phylogenetic comparison JOURNAL OF EXPERIMENTAL BIOLOGY Galli, G. L., Lipnick, M. S., Shiels, H. A., Block, B. A. 2011; 214 (7): 1068-1076

    Abstract

    Specialisations in excitation-contraction coupling may have played an important role in the evolution of endothermy and high cardiac performance in scombrid fishes. We examined aspects of Ca(2+) handling in cardiomyocytes from Pacific bonito (Sarda chiliensis), Pacific mackerel (Scomber japonicus), yellowfin tuna (Thunnus albacares) and Pacific bluefin tuna (Thunnus orientalis). The whole-cell voltage-clamp technique was used to measure the temperature sensitivity of the L-type Ca(2+) channel current (I(Ca)), density, and steady-state and maximal sarcoplasmic reticulum (SR) Ca(2+) content (ssSR(load) and maxSR(load)). Current-voltage relations, peak I(Ca) density and charge density of I(Ca) were greatest in mackerel and yellowfin at all temperatures tested. I(Ca) density and kinetics were temperature sensitive in all species studied, and the magnitude of this response was not related to the thermal preference of the species. SR(load) was greater in atrial than in ventricular myocytes in the Pacific bluefin tuna, and in species that are more cold tolerant (bluefin tuna and mackerel). I(Ca) and SR(load) were particularly small in bonito, suggesting the Na(+)/Ca(2+) exchanger plays a more pivotal role in Ca(2+) entry into cardiomyocytes of this species. Our comparative approach reveals that the SR of cold-tolerant scombrid fishes has a greater capacity for Ca(2+) storage. This specialisation may contribute to the temperature tolerance and thermal niche expansion of the bluefin tuna and mackerel.

    View details for DOI 10.1242/jeb.048231

    View details for Web of Science ID 000288155200011

    View details for PubMedID 21389190

    View details for PubMedCentralID PMC3052253

  • Warm fish with cold hearts: thermal plasticity of excitation-contraction coupling in bluefin tuna PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Shiels, H. A., Di Maio, A., Thompson, S., Block, B. A. 2011; 278 (1702): 18-27

    Abstract

    Bluefin tuna have a unique physiology. Elevated metabolic rates coupled with heat exchangers enable bluefin tunas to conserve heat in their locomotory muscle, viscera, eyes and brain, yet their hearts operate at ambient water temperature. This arrangement of a warm fish with a cold heart is unique among vertebrates and can result in a reduction in cardiac function in the cold despite the elevated metabolic demands of endothermic tissues. In this study, we used laser scanning confocal microscopy and electron microscopy to investigate how acute and chronic temperature change affects tuna cardiac function. We examined the temporal and spatial properties of the intracellular Ca2+ transient (Δ[Ca2+]i) in Pacific bluefin tuna (Thunnus orientalis) ventricular myocytes at the acclimation temperatures of 14°C and 24°C and at a common test temperature of 19°C. Acute (less than 5 min) warming and cooling accelerated and slowed the kinetics of Δ[Ca2+]i, indicating that temperature change limits cardiac myocyte performance. Importantly, we show that thermal acclimation offered partial compensation for these direct effects of temperature. Prolonged cold exposure (more than four weeks) increased the amplitude and kinetics of Δ[Ca2+]i by increasing intracellular Ca2+ cycling through the sarcoplasmic reticulum (SR). These functional findings are supported by electron microscopy, which revealed a greater volume fraction of ventricular SR in cold-acclimated tuna myocytes. The results indicate that SR function is crucial to the performance of the bluefin tuna heart in the cold. We suggest that SR Ca2+ cycling is the malleable unit of cellular Ca2+ flux, offering a mechanism for thermal plasticity in fish hearts. These findings have implications beyond endothermic fish and may help to delineate the key steps required to protect vertebrate cardiac function in the cold.

    View details for DOI 10.1098/rspb.2010.1274

    View details for Web of Science ID 000284554800004

    View details for PubMedID 20667881

    View details for PubMedCentralID PMC2992732

  • , off California using dorsal fins. Marine biology Anderson, S. D., Chapple, T. K., Jorgensen, S. J., Klimley, A. P., Block, B. A. 2011; 158 (6): 1233-1237

    Abstract

    Mark-recapture techniques can be used to estimate white shark (Carcharodon carcharias) population abundance. These frameworks are based on assumptions that marks are conserved and animals are present at the sampling location over the entire duration of the study. Though these assumptions have been validated across short-time scales for white sharks, long-term studies of population trends are dependent on these assumptions being valid across longer periods. We use 22 years of photographic data from aggregation sites in central California to support the use of dorsal fin morphology as long-term individual identifiers. We identified five individuals over 16-22 years, which support the use of dorsal fins as long-time individual identifiers, illustrate strong yearly site fidelity to coastal aggregation sites across extended time periods (decades), and provide the first empirical validation of white shark longevity >22 years. These findings support the use of fin morphology in mark-recapture frameworks for white sharks.

    View details for PubMedID 24391267

  • Vertical and horizontal habitat preferences of post-nesting leatherback turtles in the South Pacific Ocean MARINE ECOLOGY PROGRESS SERIES Shillinger, G. L., Swithenbank, A. M., Bailey, H., Bograd, S. J., Castelton, M. R., Wallace, B. P., Spotila, J. R., Paladino, F. V., Piedra, R., Block, B. A. 2011; 422: 275-289

    View details for DOI 10.3354/meps08884

    View details for Web of Science ID 000286933500025

  • Movements and behaviors of swordfish in the Atlantic and Pacific Oceans examined using pop-up satellite archival tags FISHERIES OCEANOGRAPHY Dewar, H., Prince, E. D., Musyl, M. K., Brill, R. W., Sepulveda, C., Luo, J., Foley, D., Orbesen, E. S., Domeier, M. L., Nasby-Lucas, N., Snodgrass, D., Laurs, R. M., Hoolihan, J. P., Block, B. A., McNaughton, L. M. 2011; 20 (3): 219-241
  • Expression of cytokines IL-1 beta and TNF-alpha in tissues and cysts surrounding Didymocystis wedli (Digenea, Didymozoidae) in the Pacific bluefin tuna (Thunnus orientalis) FISH & SHELLFISH IMMUNOLOGY Mladineo, I., Block, B. A. 2010; 29 (3): 487-493

    Abstract

    Tuna long distance migrations and exposure to wide range of ambient water temperatures facilitate infections with several parasitic groups. This is reflected in the remarkable diversity of tuna parasite communities, especially members of Didymozoidae superfamily (Poche, 1907) (Trematoda, Digenea). Didymocystis wedli is the most frequent species encountered in bluefin tuna parasitizing gill filaments, therefore suggested as a biological marker to differentiate between discrete tuna Atlantic stocks. Because of its high occurrence in gill tissue and inflammatory reaction as the consequence, the aim of our study was to asses if inflammatory madiation through expression of IL-1beta and TNF-alpha is present locally at the site of D. wedli encystment, as well as if the systematic expression of cytokines can be detected in different tissues of infected versus uninfected fish. Quantification of localized cytokine expression was done on paraffine embedded gill sections by in situ hybridization, while quantitative PCR was used to mesured cytokine transcripts in skin mucus, kidney, spleen, gills and liver. Our results suggest that tuna constitutive expression of IL-1beta and TNF-alpha in gills and skin implies a well-adapted innate immunity present at the barrier between the organism and environment. Upregulation of both cytokines in Didymocystis-infected gills not followed by a systematic response evidences the ongoing of an inflammatory process specific for the parasitation site. However, the lack of intensive cytokines response to D. wedli observed by molecular and histological data that fails to eliminate the parasite, could be related to the "old" age of the parasitic process.

    View details for DOI 10.1016/j.fsi.2010.05.008

    View details for Web of Science ID 000280513700014

    View details for PubMedID 20580835

  • Postprandial metabolism of Pacific bluefin tuna (Thunnus orientalis) JOURNAL OF EXPERIMENTAL BIOLOGY Clark, T. D., Brandt, W. T., Nogueira, J., Rodriguez, L. E., Price, M., Farwell, C. J., Block, B. A. 2010; 213 (14): 2379-2385

    Abstract

    Specific dynamic action (SDA) is defined as the energy expended during ingestion, digestion, absorption and assimilation of a meal. This study presents the first data on the SDA response of individual tunas of any species. Juvenile Pacific bluefin tunas (Thunnus orientalis; body mass 9.7-11.0 kg; N=7) were individually fed known quantities of food consisting primarily of squid and sardine (meal energy range 1680-8749 kJ, approximately 4-13% of tuna body mass). Oxygen consumption rates (M(O2)) were measured in a swim tunnel respirometer during the postprandial period at a swimming speed of 1 body length (BL) s(-1) and a water temperature of 20 degrees C. was markedly elevated above routine levels in all fish following meal consumption [routine metabolic rate (RMR)=174+/-9 mg kg(-1) h(-1)]. The peak M(O2) during the SDA process ranged from 250 to 440 mg kg(-1) h(-1) (1.5-2.3 times RMR) and was linearly related to meal energy content. The duration of the postprandial increment in M(O2) ranged from 21 h to 33 h depending upon meal energy content. Consequently, the total energy used in SDA increased linearly with meal energy and ranged from 170 kJ to 688 kJ, such that the SDA process accounted for 9.2+/-0.7% of ingested energy across all experiments. These values suggest rapid and efficient food conversion in T. orientalis in comparison with most other fishes. Implanted archival temperature tags recorded the increment in visceral temperature (T(V)) in association with SDA. M(O2) returned to routine levels at the end of the digestive period 2-3 h earlier than T(V). The qualitative patterns in M(O2) and T(V) during digestion were similar, strengthening the possibility that archival measurements of T(V) can provide new insight into the energetics and habitat utilization of free-swimming bluefin in the natural environment. Despite efficient food conversion, SDA is likely to represent a significant component of the daily energy budget of wild bluefin tunas due to a regular and high ingestion of forage.

    View details for DOI 10.1242/jeb.043455

    View details for Web of Science ID 000279180700009

    View details for PubMedID 20581267

  • Comparative Influence of Ocean Conditions on Yellowfin and Atlantic Bluefin Tuna Catch from Longlines in the Gulf of Mexico PLOS ONE Teo, S. L., Block, B. A. 2010; 5 (5)

    Abstract

    Directed fishing effort for Atlantic bluefin tuna in the Gulf of Mexico (GOM), their primary spawning grounds in the western Atlantic, has been prohibited since the 1980s due to a precipitous decline of the spawning stock biomass. However, pelagic longlines targeted at other species, primarily yellowfin tuna and swordfish, continue to catch Atlantic bluefin tuna in the GOM as bycatch. Spatial and temporal management measures minimizing bluefin tuna bycatch in the GOM will likely become important in rebuilding the western Atlantic bluefin stock. In order to help inform management policy and understand the relative distribution of target and bycatch species in the GOM, we compared the spatiotemporal variability and environmental influences on the catch per unit effort (CPUE) of yellowfin (target) and bluefin tuna (bycatch). Catch and effort data from pelagic longline fisheries observers (1993-2005) and scientific tagging cruises (1998-2002) were coupled with environmental and biological data. Negative binomial models were used to fit the data for both species and Akaike's Information Criterion (corrected for small sample size) was used to determine the best model. Our results indicate that bluefin CPUE had higher spatiotemporal variability as compared to yellowfin CPUE. Bluefin CPUE increased substantially during the breeding months (March-June) and peaked in April and May, while yellowfin CPUE remained relatively high throughout the year. In addition, bluefin CPUE was significantly higher in areas with negative sea surface height anomalies and cooler sea surface temperatures, which are characteristic of mesoscale cyclonic eddies. In contrast, yellowfin CPUE was less sensitive to environmental variability. These differences in seasonal variability and sensitivity to environmental influences suggest that bluefin tuna bycatch in the GOM can be reduced substantially by managing the spatial and temporal distribution of the pelagic longline effort without substantially impacting yellowfin tuna catches.

    View details for DOI 10.1371/journal.pone.0010756

    View details for Web of Science ID 000278222100001

    View details for PubMedID 20526356

    View details for PubMedCentralID PMC2878315

  • Multilocus phylogenetic analyses reveal that habitat selection drives the speciation of Didymozoidae (Digenea) parasitizing Pacific and Atlantic bluefin tunas PARASITOLOGY Mladineo, I., Bott, N. J., Nowak, B. F., Block, B. A. 2010; 137 (6): 1013-1025

    Abstract

    Parasite communities of wild and reared bluefin tuna display remarkable diversity. Among these, the most prevalent and abundant are the Didymozoidae (Monticelli, 1888) (Trematoda, Digenea), considered one of the most taxonomically complex digenean families. The aim of this study was to evaluate phylogenetic structure of Didymozoidae occurring in Pacific (Thunnus orientalis) and Atlantic bluefin tuna (T. thynnus) in order to increase our knowledge of didymozoid zoogeography and identify species that could successfully be employed as biological tags for stock assessment studies. For the present analyses we used 2 nuclear ribosomal DNA loci, part of the 28S gene and the second internal transcribed spacer (ITS-2) as well as a portion of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1). In most parasitic groups, morphology is the primary factor in the structuring of phylogenetic relationships. In rare examples, however, habitat has been suggested as a primary factor affecting parasite evolution. During their evolution, didymozoids have spread and inhabited a remarkable number of different sites in their hosts, colonizing exterior as well as strictly interior niches. Our data suggest that habitat selection has been the leading force in shaping didymozoid phylogenetic relationships. For 2 didymozoid species (D. wedli and D. palati), cox1 sequences indicate intraspecific differences between Mexican and Adriatic populations.

    View details for DOI 10.1017/S0031182009991703

    View details for Web of Science ID 000278673600012

    View details for PubMedID 20028607

  • Philopatry and migration of Pacific white sharks PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES Jorgensen, S. J., Reeb, C. A., Chapple, T. K., Anderson, S., Perle, C., Van Sommeran, S. R., Fritz-Cope, C., Brown, A. C., Klimley, A. P., Block, B. A. 2010; 277 (1682): 679-688

    Abstract

    Advances in electronic tagging and genetic research are making it possible to discern population structure for pelagic marine predators once thought to be panmictic. However, reconciling migration patterns and gene flow to define the resolution of discrete population management units remains a major challenge, and a vital conservation priority for threatened species such as oceanic sharks. Many such species have been flagged for international protection, yet effective population assessments and management actions are hindered by lack of knowledge about the geographical extent and size of distinct populations. Combining satellite tagging, passive acoustic monitoring and genetics, we reveal how eastern Pacific white sharks (Carcharodon carcharias) adhere to a highly predictable migratory cycle. Individuals persistently return to the same network of coastal hotspots following distant oceanic migrations and comprise a population genetically distinct from previously identified phylogenetic clades. We hypothesize that this strong homing behaviour has maintained the separation of a northeastern Pacific population following a historical introduction from Australia/New Zealand migrants during the Late Pleistocene. Concordance between contemporary movement and genetic divergence based on mitochondrial DNA demonstrates a demographically independent management unit not previously recognized. This population's fidelity to discrete and predictable locations offers clear population assessment, monitoring and management options.

    View details for DOI 10.1098/rspb.2009.1155

    View details for Web of Science ID 000273882800004

    View details for PubMedID 19889703

    View details for PubMedCentralID PMC2842735

  • The economic efficiency of a time-area closure to protect spawning bluefin tuna JOURNAL OF APPLIED ECOLOGY Armsworth, P. R., Block, B. A., Eagle, J., Roughgarden, J. E. 2010; 47 (1): 36-46
  • Movements and diving behavior of Atlantic bluefin tuna Thunnus thynnus in relation to water column structure in the northwestern Atlantic MARINE ECOLOGY PROGRESS SERIES Lawson, G. L., Castleton, M. R., Block, B. A. 2010; 400: 245-265

    View details for DOI 10.3354/meps08394

    View details for Web of Science ID 000275528300021

  • Resource partitioning by species but not sex in sympatric boobies in the central Pacific Ocean MARINE ECOLOGY PROGRESS SERIES Young, H. S., Shaffer, S. A., McCauley, D. J., Foley, D. G., Dirzo, R., Block, B. A. 2010; 403: 291-301

    View details for DOI 10.3354/meps08478

    View details for Web of Science ID 000276799000024

  • Effect of thermal acclimation on action potentials and sarcolemmal K+ channels from Pacific bluefin tuna cardiomyocytes AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Galli, G. L., Lipnick, M. S., Block, B. A. 2009; 297 (2): R502-R509

    Abstract

    To sustain cardiac muscle contractility relatively independent of temperature, some fish species are capable of temporarily altering excitation-contraction coupling processes to meet the demands of their environment. The Pacific bluefin tuna, Thunnus orientalis, is a partially endothermic fish that inhabits a wide range of thermal niches. The present study examined the effects of temperature and thermal acclimation on sarcolemmal K(+) currents and their role in action potential (AP) generation in bluefin tuna cardiomyocytes. Atrial and ventricular myocytes were enzymatically isolated from cold (14 degrees C)- and warm (24 degrees C)-acclimated bluefin tuna. APs and current-voltage relations of K(+) channels were measured using the whole cell current and voltage clamp techniques, respectively. Data were collected either at the cardiomyocytes' respective acclimation temperature of 14 or 24 degrees C or at a common test temperature of 19 degrees C (to reveal the effects of acclimation). AP duration (APD) was prolonged in cold-acclimated (CA) cardiomyocytes tested at 14 degrees C compared with 19 degrees C and in warm-acclimated (WA) cardiomyocytes tested at 19 degrees C compared with 24 degrees C. This effect was mirrored by a decrease in the density of the delayed-rectifier current (I(Kr)), whereas the density of the background inward-rectifier current (I(K1)) was unchanged. When CA and WA cardiomyocytes were tested at a common temperature of 19 degrees C, no significant effects of temperature acclimation on AP shape or duration were observed, whereas I(Kr) density was markedly increased in CA cardiomyocytes. I(K1) density was unaffected in CA ventricular myocytes but was significantly reduced in CA atrial myocytes, resulting in a depolarization of atrial resting membrane potential. Our results indicate the bluefin AP is relatively short compared with other teleosts, which may allow the bluefin heart to function at cold temperatures without the necessity for thermal compensation of APD.

    View details for DOI 10.1152/ajpregu.90810.2008

    View details for Web of Science ID 000268187100031

    View details for PubMedID 19515982

  • Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags PLOS ONE Walli, A., Teo, S. L., Boustany, A., Farwell, C. J., Williams, T., Dewar, H., Prince, E., Block, B. A. 2009; 4 (7)

    Abstract

    Electronic tags were used to examine the seasonal movements, aggregations and diving behaviors of Atlantic bluefin tuna (Thunnus thynnus) to better understand their migration ecology and oceanic habitat utilization. Implantable archival tags (n = 561) were deployed in bluefin tuna from 1996 to 2005 and 106 tags were recovered. Movement paths of the fish were reconstructed using light level and sea-surface-temperature-based geolocation estimates. To quantify habitat utilization we employed a weighted kernel estimation technique that removed the biases of deployment location and track length. Throughout the North Atlantic, high residence times (167+/-33 days) were identified in four spatially confined regions on a seasonal scale. Within each region, bluefin tuna experienced distinct temperature regimes and displayed different diving behaviors. The mean diving depths within the high-use areas were significantly shallower and the dive frequency and the variance in internal temperature significantly higher than during transit movements between the high-use areas. Residence time in the more northern latitude high-use areas was significantly correlated with levels of primary productivity. The regions of aggregation are associated with areas of abundant prey and potentially represent critical foraging habitats that have seasonally abundant prey. Throughout the North Atlantic mean diving depth was significantly correlated with the depth of the thermocline, and dive behavior changed in relation to the stratification of the water column. In this study, with numerous multi-year tracks, there appear to be repeatable patterns of clear aggregation areas that potentially are changing with environmental conditions. The high concentrations of bluefin tuna in predictable locations indicate that Atlantic bluefin tuna are vulnerable to concentrated fishing efforts in the regions of foraging aggregations.

    View details for DOI 10.1371/journal.pone.0006151

    View details for Web of Science ID 000267806400007

    View details for PubMedID 19582150

    View details for PubMedCentralID PMC2701635

  • Expression of Hsp70, Na+/K+ ATP-ase, HIF-1 alpha, IL-1 beta and TNF-alpha in captive Pacific bluefin tuna (Thunnus orientalis) after chronic warm and cold exposure JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY Mladineo, I., Block, B. A. 2009; 374 (1): 51-57
  • Heterologous hybridization to a complementary DNA microarray reveals the effect of thermal acclimation in the endothermic bluefin tuna (Thunnus orientalis) MOLECULAR ECOLOGY Castilho, P. C., Buckley, B. A., Somero, G., Block, B. A. 2009; 18 (10): 2092-2102

    Abstract

    The temperature stress that pelagic fishes experience can induce physiological and behavioural changes that leave a signature in gene expression profiles. We used a functional genomics approach to identify genes that were up- or down-regulated following thermal stress in the Pacific bluefin tuna. Following the acclimation period, 113, 81 and 196 genes were found to be differentially expressed between the control (20 degrees C) and cold (15 degrees) treatment groups, in ventricle, red muscle and white muscle, respectively. The genes whose expression levels were responsive to thermal acclimation varied according to muscle fibre type, perhaps reflecting the tissue-specific degrees of endothermy characteristic of this species.

    View details for DOI 10.1111/j.1365-294X.2009.04174.x

    View details for Web of Science ID 000265774300005

    View details for PubMedID 19389180

  • Habitat and behaviour of yellowfin tuna Thunnus albacares in the Gulf of Mexico determined using pop-up satellite archival tags JOURNAL OF FISH BIOLOGY Weng, K. C., Stokesbury, M. J., Boustany, A. M., Seitz, A. C., Teo, S. L., Miller, S. K., Block, B. A. 2009; 74 (7): 1434-1449

    Abstract

    This study presents the first data on movement, habitat use and behaviour for yellowfin tuna Thunnus albacares in the Atlantic Basin. Six individuals were tracked in the Gulf of Mexico using pop-up satellite archival tags. Records up to 80 days in length were obtained, providing information on depth and temperature preferences as well as horizontal movements. Thunnus albacares in the Gulf of Mexico showed a strong preference for the mixed layer and thermocline, consistent with findings for this species in other ocean basins. Fish showed a diel pattern in depth distribution, remaining in surface and mixed layer waters at night and diving to deeper waters during the day. The vertical extent of T. albacares habitat appeared to be temperature limited, with fish generally avoiding waters that were >6 degrees C cooler than surface waters. The vertical and thermal habitat usage of T. albacares differs from that of bigeye Thunnus obesus and bluefin Thunnus thynnus, Thunnus orientalis and Thunnus maccoyii tunas. These results are consistent with the results of earlier studies conducted on T. albacares in other oceans.

    View details for DOI 10.1111/j.1095-8649.2009.02209.x

    View details for Web of Science ID 000265550600006

    View details for PubMedID 20735644

  • Advances in Conservation Oceanography New Tagging and Tracking Technologies and Their Potential for Transforming the Science Underlying Fisheries Management OCEANOGRAPHY Greene, C. H., Block, B. A., Welch, D., Jackson, G., Lawson, G. L., Rechisky, E. L. 2009; 22 (1): 210-223
  • A sequential Bayesian methodology to estimate movement and exploitation rates using electronic and conventional tag data: application to Atlantic bluefin tuna (Thunnus thynnus) CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Kurota, H., McAllister, M. K., Lawson, G. L., Nogueira, J. I., Teo, S. L., Block, B. A. 2009; 66 (2): 321-342

    View details for DOI 10.1139/F08-197

    View details for Web of Science ID 000264957500013

  • Near real time satellite tracking of striped marlin (Kajikia audax) movements in the Pacific Ocean MARINE BIOLOGY Holdsworth, J. C., Sippel, T. J., Block, B. A. 2009; 156 (3): 505–14
  • Vertical Movements and Habitat Utilization of Skipjack (Katsuwonus pelamis), Yellowfin (Thunnus albacares), and Bigeye (Thunnus obesus) Tunas in the Equatorial Eastern Pacific Ocean, Ascertained Through Archival Tag Data 2nd International Symposium on Tagging and Tracking Marine Fish with Electronic Devices Schaefer, K. M., Fuller, D. W., Block, B. A. SPRINGER. 2009: 121–144
  • THERMAL PLASTICITY OF CELLULAR CALCIUM CYCLING IN BLUEFIN TUNA MYOCYTES Shiels, H., Block, B. A. SPRINGER TOKYO. 2009: 97
  • CALCIUM CYCLING IN SCOMBRID CARDIAC MYOCYTES: A PHYLOGENETIC COMPARISON Galli, G., Lipnick, M. S., Block, B. A. SPRINGER TOKYO. 2009: 540
  • Estimating chlorophyll profiles from electronic tags deployed on pelagic animals AQUATIC BIOLOGY Teo, S. L., Kudela, R. M., Rais, A., Perle, C., Costa, D. P., Block, B. A. 2009; 5 (2): 195-207

    View details for DOI 10.3354/ab00152

    View details for Web of Science ID 000266737900010

  • An oceanographic context for the foraging ecology of eastern Pacific leatherback turtles: Consequences of ENSO (vol 55, pg 646, 2008) DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS Saba, V. S., Shillinger, G. L., Swithenbank, A. M., Block, B. A., Spotila, J. R., Musick, J. A., Paladino, F. V. 2008; 55 (12): 1748
  • Mitochondrial DNA and electronic tracking reveal population structure of Atlantic bluefin tuna (Thunnus thynnus) MARINE BIOLOGY Boustany, A. M., Reeb, C. A., Block, B. A. 2008; 156 (1): 13-24
  • Natal Homing and Connectivity in Atlantic Bluefin Tuna Populations SCIENCE Rooker, J. R., Secor, D. H., De Metrio, G., Schloesser, R., Block, B. A., Neilson, J. D. 2008; 322 (5902): 742–44

    Abstract

    Atlantic bluefin tuna populations are in steep decline, and an improved understanding of connectivity between individuals from eastern (Mediterranean Sea) and western (Gulf of Mexico) spawning areas is needed to manage remaining fisheries. Chemical signatures in the otoliths of yearlings from regional nurseries were distinct and served as natural tags to assess natal homing and mixing. Adults showed high rates of natal homing to both eastern and western spawning areas. Trans-Atlantic movement (east to west) was significant and size-dependent, with individuals of Mediterranean origin mixing with the western population in the U.S. Atlantic. The largest (oldest) bluefin tuna collected near the northern extent of their range in North American waters were almost exclusively of western origin, indicating that this region represents critical habitat for the western population.

    View details for DOI 10.1126/science.1161473

    View details for Web of Science ID 000260605200049

    View details for PubMedID 18832611

  • Ultrastructure of the sarcoplasmic reticulum in cardiac myocytes from Pacific bluefin tuna CELL AND TISSUE RESEARCH Di Maio, A., Block, B. A. 2008; 334 (1): 121-134

    Abstract

    Pacific bluefin tuna are active teleost fish with a large capacity for heat conservation and endothermy. They have a high metabolism, and hence the myocardium must be capable of sustaining elevated levels of cardiac output over a wide range of temperatures. To examine the way that the myocardial cells of bluefin tuna respond to their unique cardiac physiology, we have studied the ultrastructure of the internal membrane system and mitochondria of atrial and ventricular myocytes by light and electron microscopy. Our results reveal that cardiomyocytes of juvenile bluefin tuna posses a relatively high content of sarcoplasmic reticulum (SR), together with a large volume of mitochondria within the two (compact and spongy) ventricular compartments and in the atrial myocardium. The mitochondrial structure and distribution in bluefin tuna myocardium follow specific metabolic zonation resulting in a higher volume and lower cristae density in the compact ventricular layer than in atrium and spongy layer. The presence of junctional SR profiles and an extensive network of free SR within cells may ensure a rapid delivery of Ca(2+) to the myofibrils. This, in conjunction with transarcolemmal Ca(2+) entry, might contribute to a faster excitation-contraction-relaxation cycle and thus enhance cardiac performance, cardiac output, and the maintenance of excitability at low temperatures. We propose that the mitochondrial configuration together with the developed SR ultrastructure of bluefin tunas myocardium are important evolutionary steps for the maintenance of high heart rates and endothermy in this teleost fish.

    View details for DOI 10.1007/s00441-008-0669-6

    View details for Web of Science ID 000259141500013

    View details for PubMedID 18688649

  • Persistent leatherback turtle migrations present opportunities for conservation PLOS BIOLOGY Shillinger, G. L., Palacios, D. M., Bailey, H., Bograd, S. J., Swithenbank, A. M., Gaspar, P., Wallace, B. P., Spotila, J. R., Paladino, F. V., Piedra, R., Eckert, S. A., Block, B. A. 2008; 6 (7): 1408-1416

    Abstract

    Effective transboundary conservation of highly migratory marine animals requires international management cooperation as well as clear scientific information about habitat use by these species. Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by >90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality. While research and conservation efforts on nesting beaches are ongoing, relatively little is known about this population of leatherbacks' oceanic habitat use and migration pathways. We present the largest multi-year (2004-2005, 2005-2006, and 2007) satellite tracking dataset (12,095 cumulative satellite tracking days) collected for leatherback turtles. Forty-six females were electronically tagged during three field seasons at Playa Grande, Costa Rica, the largest extant nesting colony in the eastern Pacific. After completing nesting, the turtles headed southward, traversing the dynamic equatorial currents with rapid, directed movements. In contrast to the highly varied dispersal patterns seen in many other sea turtle populations, leatherbacks from Playa Grande traveled within a persistent migration corridor from Costa Rica, past the equator, and into the South Pacific Gyre, a vast, low-energy, low-productivity region. We describe the predictable effects of ocean currents on a leatherback migration corridor and characterize long-distance movements by the turtles in the eastern South Pacific. These data from high seas habitats will also elucidate potential areas for mitigating fisheries bycatch interactions. These findings directly inform existing multinational conservation frameworks and provide immediate regions in the migration corridor where conservation can be implemented. We identify high seas locations for focusing future conservation efforts within the leatherback dispersal zone in the South Pacific Gyre.

    View details for DOI 10.1371/journal.pbio.0060171

    View details for Web of Science ID 000257971100013

    View details for PubMedID 18630987

    View details for PubMedCentralID PMC2459209

  • Thermal acclimation confers no tolerance to acute temperature change in cardiac myocytes from bluefin tuna Galli, G., Shiels, H., Block, B. FEDERATION AMER SOC EXP BIOL. 2008
  • Using skin mucus RNA to study gene expression in pacific bluefin tuna Castilho, P., Jayasundara, N., Mladineo, I., Block, B. B. FEDERATION AMER SOC EXP BIOL. 2008
  • Migration of an upper trophic level predator, the salmon shark Lamna ditropis, between distant ecoregions MARINE ECOLOGY PROGRESS SERIES Weng, K. C., Foley, D. G., Ganong, J. E., Perle, C., Shillinger, G. L., Block, B. A. 2008; 372: 253-264

    View details for DOI 10.3354/meps07706

    View details for Web of Science ID 000262418100024

  • Temperature effects on metabolic rate of juvenile Pacific bluefin tuna Thunnus orientalis JOURNAL OF EXPERIMENTAL BIOLOGY Blank, J. M., Morrissette, J. M., Farwell, C. J., Price, M., Schallert, R. J., Block, B. A. 2007; 210 (23): 4254-4261

    Abstract

    Pacific bluefin tuna inhabit a wide range of thermal environments across the Pacific ocean. To examine how metabolism varies across this thermal range, we studied the effect of ambient water temperature on metabolic rate of juvenile Pacific bluefin tuna, Thunnus thynnus, swimming in a swim tunnel. Rate of oxygen consumption (MO2) was measured at ambient temperatures of 8-25 degrees C and swimming speeds of 0.75-1.75 body lengths (BL) s(-1). Pacific bluefin swimming at 1 BL s(-1) per second exhibited a U-shaped curve of metabolic rate vs ambient temperature, with a thermal minimum zone between 15 degrees C to 20 degrees C. Minimum MO2 of 175+/-29 mg kg(-1) h(-1) was recorded at 15 degrees C, while both cold and warm temperatures resulted in increased metabolic rates of 331+/-62 mg kg(-1) h(-1) at 8 degrees C and 256+/-19 mg kg(-1) h(-1) at 25 degrees C. Tailbeat frequencies were negatively correlated with ambient temperature. Additional experiments indicated that the increase in MO2 at low temperature occurred only at low swimming speeds. Ambient water temperature data from electronic tags implanted in wild fish indicate that Pacific bluefin of similar size to the experimental fish used in the swim tunnel spend most of their time in ambient temperatures in the metabolic thermal minimum zone.

    View details for DOI 10.1242/jeb.005835

    View details for Web of Science ID 000251108300025

    View details for PubMedID 18025023

  • Oceanographic preferences of Atlantic bluefin tuna, Thunnus thynnus, on their Gulf of Mexico breeding grounds MARINE BIOLOGY Teo, S. L., Boustany, A. M., Block, B. A. 2007; 152 (5): 1105-1119
  • Elevated Ca2+ ATPase (SERCA2) activity in tuna hearts: Comparative aspects of temperature dependence Castilho, P. C., Landeira-Femandez, A. M., Morrissette, J., Block, B. A. ELSEVIER SCIENCE INC. 2007: 124–32

    Abstract

    Tunas have an extraordinary physiology including elevated metabolic rates and high cardiac performance. In some species, retention of metabolic heat warms the slow oxidative swimming muscles and visceral tissues. In all tunas, the heart functions at ambient temperature. Enhanced rates of calcium transport in tuna myocytes are associated with increased expression of proteins involved in the contraction-relaxation cycle. The cardiac SR Ca2+-ATPase (SERCA2) plays a major role during cardiac excitation-contraction (E-C) coupling. Measurements of oxalate-supported Ca2+-uptake in atrial SR vesicles isolated from four species of tunas indicate that bluefin have at least two fold higher Ca2+-uptake than all other tunas examined between 5 and 30 degrees C. The highest atrial Ca2+-uptake was measured in bluefin tuna at 30 degrees C (23.32+/-1.58 nmol Ca2+/mg/min). Differences among tunas in the temperature dependency of Ca2+-uptake were similar for ATP hydrolysis. Western blot analysis revealed a significant increase in SERCA2 content associated with higher Ca2+ uptake rates in the atrial tissues of bluefin tuna and similar RyR expression across species. We propose that the expression of EC coupling proteins in cardiac myocytes, and the higher rates of SERCA2 activity are an important evolutionary step for the maintenance of higher heart rates and endothermy in bluefin tuna.

    View details for DOI 10.1016/j.cbpa.2007.03.033

    View details for Web of Science ID 000249103900014

    View details for PubMedID 17566775

  • Movements, behavior, and habitat utilization of yellowfin tuna (Thunnus albacares) in the northeastern Pacific Ocean, ascertained through archival tag data MARINE BIOLOGY Schaefer, K. M., Fuller, D. W., Block, B. A. 2007; 152 (3): 503-525
  • Migration and habitat of white sharks (Carcharodon carcharias) in the eastern Pacific Ocean MARINE BIOLOGY Weng, K. C., Boustany, A. M., Pyle, P., Anderson, S. D., Brown, A., Block, B. A. 2007; 152 (4): 877-894
  • Influence of swimming speed on metabolic rates of juvenile Pacific bluefin tuna and yellowfin tuna PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY Blank, J. M., Farwell, C. J., Morrissette, J. M., Schallert, R. J., Block, B. A. 2007; 80 (2): 167-177

    Abstract

    Bluefin tuna are endothermic and have higher temperatures, heart rates, and cardiac outputs than tropical tuna. We hypothesized that the increased cardiovascular capacity to deliver oxygen in bluefin may be associated with the evolution of higher metabolic rates. This study measured the oxygen consumption of juvenile Pacific bluefin Thunnus orientalis and yellowfin tuna Thunnus albacares swimming in a swim-tunnel respirometer at 20 degrees C. Oxygen consumption (Mo2) of bluefin (7.1-9.4 kg) ranged from 235+/-38 mg kg(-1) h(-1) at 0.85 body length (BL) s(-1) to 498+/-55 mg kg(-1) h(-1) at 1.80 BL s(-1). Minimal metabolic rates of swimming bluefin were 222+/-24 mg O(2) kg(-1) h(-1) at speeds of 0.75 to 1.0 BL s(-1). Mo2 of T. albacares (3.7-7.4 kg) ranged from 164+/-18 mg kg(-1) h(-1) at 0.65 BL s(-1) to 405+/-105 mg kg(-1) h(-1) at 1.8 BL s(-1). Bluefin tuna had higher metabolic rates than yellowfin tuna at all swimming speeds tested. At a given speed, bluefin had higher metabolic rates and swam with higher tailbeat frequencies and shorter stride lengths than yellowfin. The higher M dot o2 recorded in Pacific bluefin tuna is consistent with the elevated cardiac performance and enhanced capacity for excitation-contraction coupling in cardiac myocytes of these fish. These physiological traits may underlie thermal-niche expansion of bluefin tuna relative to tropical tuna species.

    View details for Web of Science ID 000243966400001

    View details for PubMedID 17252513

  • Annual migrations, diving behavior, and thermal biology of Atlantic bluefin tuna, Thunnus thynnus, on their Gulf of Mexico breeding grounds MARINE BIOLOGY Teo, S. L., Boustany, A., Dewar, H., Stokesbury, M. J., Weng, K. C., Beemer, S., Seitz, A. C., Farwell, C. J., Prince, E. D., Block, B. A. 2007; 151 (1): 1-18
  • High apex predator biomass on remote Pacific islands CORAL REEFS Stevenson, C., Katz, L. S., Micheli, F., Block, B., Heiman, K. W., Perle, C., Weng, K., Dunbar, R., Witting, J. 2007; 26 (1): 47-51
  • Movements, behavior and habitat preferences of juvenile white sharks Carcharodon carcharias in the eastern Pacific MARINE ECOLOGY PROGRESS SERIES Weng, K. C., O'Sullivan, J. B., Lowe, C. G., Winkler, C. E., Dewar, H., Block, B. A. 2007; 338: 211-224
  • Striped marlin (Tetrapturus audax) movements and habitat utilization during a summer and autumn in the Southwest Pacific Ocean FISHERIES OCEANOGRAPHY Sippel, T. J., Davie, P. S., Holdsworth, J. C., Block, B. A. 2007; 16 (5): 459-472
  • Life history and stock structure of Atlantic bluefin tuna (Thunnus thynnus) REVIEWS IN FISHERIES SCIENCE Rooker, J. R., Bremer, J. R., Block, B. A., Dewar, H., De Metrio, G., Corriero, A., Kraus, R. T., Prince, E. D., Rodriguez-Marin, E., Secor, D. H. 2007; 15 (4): 265-310
  • Horizontal and vertical movements of juvenile bluefin tuna (Thunnus orientalis) in relation to seasons and oceanographic conditions in the eastern Pacific Ocean FISHERIES OCEANOGRAPHY Kitagawa, T., Boustany, A. M., Farwell, C. J., Williams, T. D., Castleton, M. R., Block, B. A. 2007; 16 (5): 409-421
  • Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Shaffer, S. A., Tremblay, Y., Weimerskirch, H., Scott, D., Thompson, D. R., Sagar, P. M., Moller, H., Taylor, G. A., Foley, D. G., Block, B. A., Costa, D. P. 2006; 103 (34): 12799-12802

    Abstract

    Electronic tracking tags have revolutionized our understanding of broad-scale movements and habitat use of highly mobile marine animals, but a large gap in our knowledge still remains for a wide range of small species. Here, we report the extraordinary transequatorial postbreeding migrations of a small seabird, the sooty shearwater, obtained with miniature archival tags that log data for estimating position, dive depth, and ambient temperature. Tracks (262+/-23 days) reveal that shearwaters fly across the entire Pacific Ocean in a figure-eight pattern while traveling 64,037+/-9,779 km roundtrip, the longest animal migration ever recorded electronically. Each shearwater made a prolonged stopover in one of three discrete regions off Japan, Alaska, or California before returning to New Zealand through a relatively narrow corridor in the central Pacific Ocean. Transit rates as high as 910+/-186 km.day-1 were recorded, and shearwaters accessed prey resources in both the Northern and Southern Hemisphere's most productive waters from the surface to 68.2 m depth. Our results indicate that sooty shearwaters integrate oceanic resources throughout the Pacific Basin on a yearly scale. Sooty shearwater populations today are declining, and because they operate on a global scale, they may serve as an important indicator of climate change and ocean health.

    View details for DOI 10.1073/pnas.0603715103

    View details for Web of Science ID 000240035900029

    View details for PubMedID 16908846

    View details for PubMedCentralID PMC1568927

  • Linking high metabolic rates, enhanced cardiac E-C coupling, and cold tolerance in tunas Morrissette, J. M., Blank, J. M., Castilho, P. C., Block, B. A. FEDERATION AMER SOC EXP BIOL. 2006: A829
  • Vertical and horizontal migrations by the jumbo squid Dosidicus gigas revealed by electronic tagging MARINE ECOLOGY PROGRESS SERIES Gilly, W. F., Markaida, U., Baxter, C. H., Block, B. A., Boustany, A., Zeidberg, L., Reisenbichler, K., Robison, B., Bazzino, G., SALINAS, C. 2006; 324: 1-17
  • Movement and environmental preferences of Greenland sharks (Somniosus microcephalus) electronically tagged in the St. Lawrence Estuary, Canada MARINE BIOLOGY Stokesbury, M. J., Harvey-Clark, C., Gallant, J., Block, B. A., Myers, R. A. 2005; 148 (1): 159-165
  • Satellite tagging and cardiac physiology reveal niche expansion in salmon sharks SCIENCE Weng, K. C., Castilho, P. C., Morrissette, J. M., Landeira-Fernandez, A. M., Holts, D. B., Schallert, R. J., Goldman, K. J., Block, B. A. 2005; 310 (5745): 104-106

    Abstract

    Shark populations are declining globally, yet the movements and habitats of most species are unknown. We used a satellite tag attached to the dorsal fin to track salmon sharks (Lamna ditropis) for up to 3.2 years. Here we show that salmon sharks have a subarctic-to-subtropical niche, ranging from 2 degrees to 24 degrees C, and they spend winter periods in waters as cold as 2 degrees to 8 degrees C. Functional assays and protein gels reveal that the expression of excitation-contraction coupling proteins is enhanced in salmon shark hearts, which may underlie the shark's ability to maintain heart function at cold temperatures and their niche expansion into subarctic seas.

    View details for DOI 10.1126/science.1114616

    View details for Web of Science ID 000232477000047

    View details for PubMedID 16210538

  • Comparison of light- and SST-based geolocation with satellite telemetry in free-ranging albatrosses MARINE BIOLOGY Shaffer, S. A., Tremblay, Y., Awkerman, J. A., Henry, R. W., Teo, S. L., ANDERSON, D. J., Croll, D. A., Block, B. A., Costa, D. P. 2005; 147 (4): 833-843
  • Uncoupling of Ca2+-ATPase from marlin heater organ and tuna deep red muscle by temperature Landeira-Fernandez, A. M., Da Costa, D. C., Morrissette, J., Block, B. ROCKEFELLER UNIV PRESS. 2005: 75A
  • Electronic tagging and population structure of Atlantic bluefin tuna NATURE Block, B. A., Teo, S. L., Walli, A., Boustany, A., Stokesbury, M. J., Farwell, C. J., Weng, K. C., Dewar, H., Williams, T. D. 2005; 434 (7037): 1121-1127

    Abstract

    Electronic tags that archive or transmit stored data to satellites have advanced the mapping of habitats used by highly migratory fish in pelagic ecosystems. Here we report on the electronic tagging of 772 Atlantic bluefin tuna in the western Atlantic Ocean in an effort to identify population structure. Reporting electronic tags provided accurate location data that show the extensive migrations of individual fish (n = 330). Geoposition data delineate two populations, one using spawning grounds in the Gulf of Mexico and another from the Mediterranean Sea. Transatlantic movements of western-tagged bluefin tuna reveal site fidelity to known spawning areas in the Mediterranean Sea. Bluefin tuna that occupy western spawning grounds move to central and eastern Atlantic foraging grounds. Our results are consistent with two populations of bluefin tuna with distinct spawning areas that overlap on North Atlantic foraging grounds. Electronic tagging locations, when combined with US pelagic longline observer and logbook catch data, identify hot spots for spawning bluefin tuna in the northern slope waters of the Gulf of Mexico. Restrictions on the time and area where longlining occurs would reduce incidental catch mortalities on western spawning grounds.

    View details for DOI 10.1038/nature03463

    View details for Web of Science ID 000228693300041

    View details for PubMedID 15858572

  • Physiological ecology in the 21st Century: Advancements in biologging Science Symposium on Integrative Biology in Honor of George A Bartholomew held at the Annual Meeting of the Society-for-Integrative-and-Comparative-Biology Block, B. A. OXFORD UNIV PRESS INC. 2005: 305–20

    Abstract

    Top pelagic predators such as tunas, sharks, marine turtles and mammals have historically been difficult to study due to their large body size and vast range over the oceanic habitat. In recent years the development of small microprocessor-based data storage tags that are surgically implanted or satellite-linked provide marine researchers a novel avenue for examining the movements, physiology and behaviors of pelagic animals in the wild. When biological and physical data obtained from the tags are combined with satellite derived sea surface temperature and ocean color data, the relationships between the movements, behaviors and physical ocean environment can be examined. Tag-bearing marine animals can function as autonomous ocean profilers providing oceanographic data wherever their long migrations take them. The biologging science is providing ecological physiologists with new insights into the seasonal movements, habitat utilization, breeding behaviors and population structures in of marine vertebrates. In addition, the data are revealing migration corridors, hot spots and physical oceanographic patterns that are key to understanding how organisms such as bluefin tunas use the open ocean environment. In the 21st century as ecosystem degradation and global warming continue to threaten the existence of species on Earth, the field of physiological ecology will play a more pivotal role in conservation biology.

    View details for Web of Science ID 000229163400011

    View details for PubMedID 21676774

  • Metabolic rate of the Pacific bluefin tuna, Thunnus orientalis Blank, J. M., Farwell, C. J., Schallert, R. J., Morrissette, J. M., Block, B. A. FEDERATION AMER SOC EXP BIOL. 2005: A213
  • Movement of Atlantic bluefin tuna (Thunnus thynnus) as determined by satellite tagging experiments initiated off New England CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES Stokesbury, M. J., Teo, S. L., Seitz, A., O'Dor, R. K., Block, B. A. 2004; 61 (10): 1976-1987

    View details for DOI 10.1139/F04-130

    View details for Web of Science ID 000226595900016

  • Intramuscular anesthesia of bonito and Pacific mackerel with ketamine and medetomidine and reversal of anesthesia with atipamezole JAVMA-JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION Williams, T. D., Rollins, M., Block, B. A. 2004; 225 (3): 417–21

    Abstract

    To determine anesthetic effects of ketamine and medetomidine in bonitos and mackerels and whether anesthesia could be reversed with atipamezole.Clinical trial.43 bonitos (Sarda chiliensis) and 47 Pacific mackerels (Scomber japonica).28 bonitos were given doses of ketamine ranging from 1 to 8 mg/kg (0.5 to 3.6 mg/lb), i.m., and doses of medetomidine ranging from 0.2 to 1.6 mg/kg (0.1 to 0.7 mg/lb), i.m. (ratio of ketamine to medetomidine, 2.5:1 to 20:1). Doses of atipamezole equal to 1 or 5 times the dose of medetomidine were used. The remaining 15 bonitos were used to determine the anesthetic effects of ketamine at a dose of 4 mg/kg (1.8 mg/lb) and medetomidine at a dose of 0.4 mg/kg (0.2 mg/lb). The mackerels were given ketamine at doses ranging from 11 to 533 mg/kg (5 to 242 mg/lb) and medetomidine at doses ranging from 0.3 to 9.1 mg/kg (0.1 to 4.1 mg/lb; ratio of ketamine to medetomidine, 3:1 to 800:1). Doses of atipamezole equal to 5 times the dose of medetomidine were used.I.m. administration of ketamine at a dose of 4 mg/kg and medetomidine at a dose of 0.4 mg/kg in bonitos and ketamine at a dose of 53 to 228 mg/kg (24 to 104 mg/lb) and medetomidine at a dose of 0.6 to 4.2 mg/kg (0.3 to 1.9 mg/lb) in mackerels was safe and effective. For both species, administration of atipamezole at a dose 5 times the dose of medetomidine reversed the anesthetic effects.Results suggest that a combination of ketamine and medetomidine can safely be used for anesthesia of bonitos and mackerels and that anesthetic effects can be reversed with atipamezole.

    View details for DOI 10.2460/javma.2004.225.417

    View details for Web of Science ID 000222907800021

    View details for PubMedID 15328719

  • Electrophysiological properties of the L-type Ca2+ current in cardiomyocytes from bluefin tuna and Pacific mackerel AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Shiels, H. A., Blank, J. M., Farrell, A. P., Block, B. A. 2004; 286 (4): R659-R668

    Abstract

    Tunas are capable of exceptionally high maximum metabolic rates; such capability requires rapid delivery of oxygen and metabolic substrate to the tissues. This requirement is met, in part, by exceptionally high maximum cardiac outputs, opening the possibility that myocardial Ca(2+) delivery is enhanced in myocytes from tuna compared with those from other fish. In this study, we investigated the electrophysiological properties of the cardiac L-type Ca(2+) channel current (I(Ca)) to test the hypothesis that Ca(2+) influx would be large and have faster kinetics in cardiomyocytes from Pacific bluefin tuna (Thunnus orientalis) than in those from its sister taxon, the Pacific mackerel (Scombe japonicus). In accordance with this hypothesis, I(Ca) in atrial myocytes from bluefin tuna had significantly greater peak current amplitudes and faster fast inactivation kinetics (-4.4 +/- 0.2 pA/pF and 25.9 +/- 1.6 ms, respectively) than those from mackerel (-2.7 +/- 0.5 pA/pF and 32.3 +/- 3.8 ms, respectively). Steady-state activation, inactivation, and recovery from inactivation were also faster in atrial myocytes from tuna than from mackerel. In ventricular myocytes, current amplitude and activation and inactivation rates were similar in both species but elevated compared with those of other teleosts. These results indicate enhanced I(Ca) in atrial myocytes from bluefin tuna compared with Pacific mackerel; this enhanced I(Ca) may be associated with elevated cardiac performance, because I(Ca) delivers the majority of Ca(2+) involved in excitation-contraction coupling in most fish hearts. Similarly, I(Ca) is enhanced in the ventricle of both species compared with other teleosts and may play a role in the robust cardiac performance of fishes of the family Scombridae.

    View details for DOI 10.1152/ajpregu.00521.2003

    View details for Web of Science ID 000220054100008

    View details for PubMedID 14656768

  • In situ cardiac performance of Pacific bluefin tuna hearts in response to acute temperature change JOURNAL OF EXPERIMENTAL BIOLOGY Blank, J. M., Morrissette, J. M., Landeira-Fernandez, A. M., Blackwell, S. B., Williams, T. D., Block, B. A. 2004; 207 (5): 881-890

    Abstract

    This study reports the cardiovascular physiology of the Pacific bluefin tuna (Thunnus orientalis) in an in situ heart preparation. The performance of the Pacific bluefin tuna heart was examined at temperatures from 30 degrees C down to 2 degrees C. Heart rates ranged from 156 beats min(-1) at 30 degrees C to 13 beats min(-1) at 2 degrees C. Maximal stroke volumes were 1.1 ml x kg(-1) at 25 degrees C and 1.3 ml x kg(-1) at 2 degrees C. Maximal cardiac outputs were 18.1 ml x kg(-1) min(-1) at 2 degrees C and 106 ml x kg(-1) min(-1) at 25 degrees C. These data indicate that cardiovascular function in the Pacific bluefin tuna exhibits a strong temperature dependence, but cardiac function is retained at temperatures colder than those tolerated by tropical tunas. The Pacific bluefin tuna's cardiac performance in the cold may be a key adaptation supporting the broad thermal niche of the bluefin tuna group in the wild. In situ data from Pacific bluefin are compared to in situ measurements of cardiac performance in yellowfin tuna and preliminary results from albacore tuna.

    View details for DOI 10.1242/jeb.00820

    View details for Web of Science ID 000189349800023

    View details for PubMedID 14747418

  • Temperature dependence of the Ca2+-ATPase (SERCA2) in the ventricles of tuna and mackerel AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Landeira-Fernandez, A. M., Morrissette, J. M., Blank, J. M., Block, B. A. 2004; 286 (2): R398-R404

    Abstract

    Recent physiological studies on the cardiovascular performance of tunas suggest that the elevated heart rates of these fish may rely on increased use of intracellular sarcoplasmic reticulum (SR) Ca2+ stores. In this study, we compare the cellular cardiac performance in endothermic tunas (bluefin, albacore, yellowfin) and their ectothermic sister taxa (mackerel) in response to acute temperature change. The cardiac sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2) plays a major role during cardiac excitation-contraction (E-C) coupling, transporting Ca2+ from the cytosol into the lumen of the SR and thus promoting the relaxation of the muscle. Measurements of oxalate-supported Ca2+ uptake in SR-enriched ventricular vesicles indicated that tunas were capable of sustaining a rate of Ca2+ uptake that was significantly higher than the mackerel. Among tunas, the cold-tolerant bluefin had the highest rates of SR Ca2+ uptake and ATPase activity. The differences among Ca2+ uptake and ATP hydrolysis rates do not seem to result from intrinsic differences between the SERCA2 present in the different tunas, as shown by their similar temperature sensitivities and similar values for activation energy. Western blots reveal that increased SERCA2 protein content is associated with the higher Ca2+ uptake and ATPase activities seen in bluefin ventricles compared with albacore, yellowfin, and mackerel. We hypothesize that a key step in the evolution of high heart rate and high metabolic rate in tunas is increased activity of the SERCA2 enzyme. We also suggest that high levels of SERCA2 in bluefin tuna hearts may be important for retaining cardiac function at cold temperatures.

    View details for DOI 10.1152/ajpregu.00392.2003

    View details for Web of Science ID 000187791500022

    View details for PubMedID 14604842

  • Validation of geolocation estimates based on light level and sea surface temperature from electronic tags MARINE ECOLOGY PROGRESS SERIES Teo, S. L., Boustany, A., Blackwell, S., Walli, A., Weng, K. C., Block, B. A. 2004; 283: 81-98
  • The bluefin tuna heart: A model for excitation-contraction coupling in the cold Morrissette, J. M., Landeira-Fernandez, A. M., Blank, J. M., Block, B. A. BIOPHYSICAL SOCIETY. 2004: 62A
  • Diel vertical migration of the bigeye thresher shark (Alopias superciliosus), a species possessing orbital retia mirabilia FISHERY BULLETIN Weng, K. C., Block, B. A. 2004; 102 (1): 221-229
  • Characterization of ryanodine receptor and Ca2+-ATPase isoforms in the thermogenic heater organ of blue marlin (Makaira nigricans) JOURNAL OF EXPERIMENTAL BIOLOGY Morrissette, J. M., Franck, J. P., Block, B. A. 2003; 206 (5): 805-812

    Abstract

    A thermogenic organ is found beneath the brain of billfishes (Istiophoridae), swordfish (Xiphiidae) and the butterfly mackerel (Scombridae). The heater organ has been shown to warm the brain and eyes up to 14 degrees C above ambient water temperature. Heater cells are derived from extraocular muscle fibers and express a modified muscle phenotype with an extensive transverse-tubule (T-tubule) network and sarcoplasmic reticulum (SR) enriched in Ca(2+)-ATPase (SERCA) pumps and ryanodine receptors (RyRs). Heater cells have a high mitochondria content but have lost most of the contractile myofilaments. Thermogenesis has been hypothesized to be associated with release and reuptake of Ca(2+). In this study, Ca(2+) fluxes in heater SR vesicles derived from blue marlin (Makaira nigricans) were measured using fura-2 fluorescence. Upon the addition of MgATP, heater SR vesicles rapidly sequestered Ca(2+). Uptake of Ca(2+) was thapsigargin sensitive, and maximum loading ranged between 0.8 micro mol Ca(2+) mg(-1) protein and 1.0 micro mol Ca(2+) mg(-1) protein. Upon the addition of 10 mmol l(-1) caffeine or 350 micro mol l(-1) ryanodine, heater SR vesicles released only a small fraction of the loaded Ca(2+). However, ryanodine could elicit a much larger Ca(2+) release event when the activity of the SERCA pumps was reduced. RNase protection assays revealed that heater tissue expresses an RyR isoform that is also expressed in fish slow-twitch skeletal muscle but is distinct from the RyR expressed in fish fast-twitch skeletal muscle. The heater and slow-twitch muscle RyR isoform has unique physiological properties. In the presence of adenine nucleotides, this RyR remains open even though cytoplasmic Ca(2+) is elevated, a condition that normally closes RyRs. The fast Ca(2+) sequestration by the heater SR, coupled with a physiologically unique RyR, is hypothesized to promote Ca(2+) cycling, ATP turnover and heat generation. A branch of the oculomotor nerve innervates heater organs, and, in this paper, we demonstrate that heater cells contain large 'endplate-like' clusters of acetylcholine receptors that appear to provide a mechanism for nervous control of thermogenesis.

    View details for DOI 10.1242/jeb.00158

    View details for Web of Science ID 000181522300002

    View details for PubMedID 12547935

  • Development of 11 microsatellite loci for population studies in the swordfish, Xiphias gladius (Teleostei : Scombridae) MOLECULAR ECOLOGY NOTES Reeb, C. A., Arcangeli, L., Block, B. A. 2003; 3 (1): 147-149
  • Revealing pelagic habitat use: the tagging of Pacific pelagics program OCEANOLOGICA ACTA Block, B. A., Costa, D. P., Boehlert, G. W., Kochevar, R. E. 2002; 25 (5): 255-266
  • Effects of temperature, epinephrine and Ca2+ on the hearts of yellowfin tuna (Thunnus albacares) JOURNAL OF EXPERIMENTAL BIOLOGY Blank, J. M., Morrissette, J. M., Davie, P. S., Block, B. A. 2002; 205 (13): 1881-1888

    Abstract

    Tuna are endothermic fish with high metabolic rates, cardiac outputs and aerobic capacities. While tuna warm their skeletal muscle, viscera, brain and eyes, their hearts remain near ambient temperature, raising the possibility that cardiac performance may limit their thermal niches. We used an in situ perfused heart preparation to investigate the effects of acute temperature change and the effects of epinephrine and extracellular Ca(2+) on cardiac function in yellowfin tuna (Thunnus albacares). Heart rate showed a strong temperature-dependence, ranging from 20 beats min(-1) at 10 degrees C to 109 beats min(-1) at 25 degrees C. Maximal stroke volume showed an inverse temperature-dependence, ranging from 1.4 ml kg(-1) at 15 degrees C to 0.9 ml kg(-1) at 25 degrees C. Maximal cardiac outputs were 27 ml kg(-1) min(-1) at 10 degrees C and 98 ml kg(-1) min(-1) at 25 degrees C. There were no significant effects of perfusate epinephrine concentrations between 1 and 100 nmol l(-1) at 20 degrees C. Increasing extracellular Ca(2+) concentration from 1.84 to 7.36 mmol l(-1) at 20 degrees C produced significant increases in maximal stroke volume, cardiac output and myocardial power output. These data demonstrate that changes in heart rate and stroke volume are involved in maintaining cardiac output during temperature changes in tuna and support the hypothesis that cardiac performance may limit the thermal niches of yellowfin tuna.

    View details for Web of Science ID 000176960600006

    View details for PubMedID 12077164

  • Behaviour of a sharptail mola in the Gulf of Mexico JOURNAL OF FISH BIOLOGY Seitz, A. C., Weng, K. C., Boustany, A. M., Block, B. A. 2002; 60 (6): 1597-1602
  • Satellite tagging - Expanded niche for white sharks NATURE Boustany, A. M., Davis, S. F., Pyle, P., Anderson, S. D., Le Boeuf, B. J., Block, B. A. 2002; 415 (6867): 35-36

    Abstract

    Until the advent of electronic tagging technology, the inherent difficulty of studying swift and powerful marine animals made ecological information about sharks of the family Lamnidae difficult to obtain. Here we report the tracking of movements of white sharks by using pop-up satellite archival tags, which reveal that their migratory movements, depth and ambient thermal ranges are wider than was previously thought.

    View details for Web of Science ID 000173028800028

  • Expanded niche for white sharks. Nature Boustany, A. M., Davis, S. F., Pyle, P., Anderson, S. D., Le Boeuf, B. J., Block, B. A. 2002; 415 (6867): 35–36

    Abstract

    Until the advent of electronic tagging technology, the inherent difficulty of studying swift and powerful marine animals made ecological information about sharks of the family Lamnidae difficult to obtain. Here we report the tracking of movements of white sharks by using pop-up satellite archival tags, which reveal that their migratory movements, depth and ambient thermal ranges are wider than was previously thought.

    View details for PubMedID 11780105

  • Migratory movements, depth preferences, and thermal biology of Atlantic bluefin tuna SCIENCE Block, B. A., Dewar, H., Blackwell, S. B., Williams, T. D., Prince, E. D., Farwell, C. J., Boustany, A., Teo, S. L., Seitz, A., Walli, A., Fudge, D. 2001; 293 (5533): 1310-1314

    Abstract

    The deployment of electronic data storage tags that are surgically implanted or satellite-linked provides marine researchers with new ways to examine the movements, environmental preferences, and physiology of pelagic vertebrates. We report the results obtained from tagging of Atlantic bluefin tuna with implantable archival and pop-up satellite archival tags. The electronic tagging data provide insights into the seasonal movements and environmental preferences of this species. Bluefin tuna dive to depths of >1000 meters and maintain a warm body temperature. Western-tagged bluefin tuna make trans-Atlantic migrations and they frequent spawning grounds in the Gulf of Mexico and eastern Mediterranean. These data are critical for the future management and conservation of bluefin tuna in the Atlantic.

    View details for Web of Science ID 000170492600038

    View details for PubMedID 11509729

  • Oxygen affinity and amino acid sequence of myoglobins from endothermic and ectothermic fish AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Marcinek, D. J., Bonaventura, J., Wittenberg, J. B., Block, B. A. 2001; 280 (4): R1123-R1133

    Abstract

    Myoglobin (Mb) buffers intracellular O2 and facilitates diffusion of O2 through the cell. These functions of Mb will be most effective when intracellular PO2 is near the partial pressure of oxygen at which Mb is half saturated (P50) of the molecule. We test the hypothesis that Mb oxygen affinity has evolved such that it is conserved when adjusted for body temperature among closely related animals. We measure oxygen P50s tonometrically and oxygen dissociation rate constants with stopped flow and generate amino acid sequence from cDNA of Mbs from fish with different body temperatures. P50s for the endothermic bluefin tuna, skipjack tuna, and blue marlin at 20 degrees C were 0.62 +/- 0.02, 0.59 +/- 0.01, 0.58 +/- 0.04 mmHg, respectively, and were significantly lower than those for ectothermic bonito (1.03 +/- 0.07 mmHg) and mackerel (1.39 +/- 0.03 mmHg). Because the oxygen affinity of Mb decreases with increasing temperature, the above differences in oxygen affinity between endothermic and ectothermic fish are reduced when adjusted for the in vivo muscle temperature of the animal. Oxygen dissociation rate constants at 20 degrees C for the endothermic species ranged from 34.1 to 49.3 s(-1), whereas those for mackerel and bonito were 102 and 62 s(-1), respectively. Correlated with the low oxygen affinity and fast dissociation kinetics of mackerel Mb is a substitution of alanine for proline that would likely result in a more flexible mackerel protein.

    View details for Web of Science ID 000167445600026

    View details for PubMedID 11247835

  • Depth and muscle temperature of Pacific bluefin tuna examined with acoustic and pop-up satellite archival tags MARINE BIOLOGY Marcinek, D. J., Blackwell, S. B., Dewar, H., Freund, E. V., Farwell, C., Dau, D., Seitz, A. C., Block, B. A. 2001; 138 (4): 869-885
  • Effect of calcium, epinephrine, and temperature on cardiac performance in yellowfin tuna Morrissette, J. M., Blank, J. M., Davie, P. S., Block, B. A. FEDERATION AMER SOC EXP BIOL. 2001: A89
  • Novel dosing regimen of eptifibatide in planned coronary stent implantation (ESPRIT): a randomised, placebo-controlled trial LANCET Tcheng, J. E., O'Shea, J. C., Cohen, E. A., Pacchiana, C. M., Kitt, M. M., Lorenz, T. J., Greenberg, S., Strony, J., Califf, R. M., Buller, C., Cantor, W. J., Joseph, D. M., Kitt, M. M., Lincoff, A. M., Madan, M., Popma, J., Teirstein, P., Cohen, E., Balleza, L., Parsons, P., Lui, H., Young, J., Fox, R., Labinaz, M., Jelley, J., Williams, J., Cohen, D., Trovato, M., Smith, J., Henry, P., Chisholm, R., O'Donnell, D., Talley, J. D., Pacheco, R., Timmis, S., Muraka, A., Mann, T., Cubeddu, G., Tannenbaum, M., Greene, J., Santoian, E., Wash, M., Sheldon, S., Pronesti, L., Jain, A., Alonzo, M., Seidelin, P., Richards, J., Lopez, M., Dittenber, R., Johnson, K., Levine, G., Maresh, K., Ferrando, T., Sarembock, I., Snyder, L., Kieval, J., Herlan, L., Miller, M., Bembridge, D., Nair, R., Hickel, L., Kiernan, F., Murphy, D., Cloutier, J., Conn, E., Beardsley, J., Ritchie, M., Cragen, D., Jafar, M. Z., Counihan, P., Rosenfelder, D., Ducas, J., Montebruno, L., Carere, R., Radons, B., Williams, L., Owens, W., Dougal, R., Feldman, R., Audrain, D., Karamali, A., Smith, M., Blankenship, J., Demko, S. L., Thompson, M., Gacoich, G., Chiodo, V., Noll, P., Ledley, G., Miller, C., Felten, W., Garner, B., Chandler, A. B., Easler, P., Albin, G., Page, A., Maddox, W., Allen, S., Gilchrist, I., Moore, R., Zimmerman, H., Curtis, M., Hildebrand, K., Greene, R., Healy, E., Meengs, W., Carson, D., George, J., Roncevich, T., Aharonian, V., Browning, R., Kostuk, W., Carr, S., Feit, F., Gostomsky, B., BUTMAN, S., Hannah, E., Hassel, C. D., Hartley, D., Shook, T., Hiller-Mullin, S., Brill, D., Dillion, M., Armstrong, B., Kerns, D., Pichard, A., Okubagzi, P., Nasser, T., Driver, L., GARRETT, J., Boltey, L., Stouffer, G., Potter, M., Amidon, T., Eggert, S., Taussig, A., Potter, K., Natarajan, M., Tartaglia, C., WERNER, J., Dunlap, T., Harrold-Runge, P., Davidson, C., Goodreau, L., Herzog, W., Calamunci, N., Slater, A., Tormey, D., Phillips, W., White, D., Sridhar, K., WHITE, J., Goodman, D., Buchbinder, M., Nasser, V., Rapeport, K., Vorman, P., Weiner, B., Borbone, M., Shadoff, N., Paap, C., Rehman, A., Haag, E., Burchenal, J., Kioussopoulos, K., Senior, D., Senior, J., Piana, R., Kirshenbaum, J., Chan, S., Chowdry, A., Kraft, P., Clark, V., Fox, M., DEUTSCH, E., Shannon, T., Quesada, R., Brotherton, J., Murrin, C., Cinderella, J., Hearne, S., Seefried, V., Farah, T., Pakstis, D., Bartolet, B., Bond, C., Debarardinis, C., Montory, D., Smith, G., Gray, D., Phillips, P., Hathaway, S., Manoukian, S., Patrick, C., Yakubov, S., Brooks, J., Block, P., Block, B., Muhlestein, J. B., Kim, S., Shalev, Y., Schmidt, W., Resar, J., Citro, K., Stine, R., Zumbuhl, J., Moreyra, A., Kreiger, S., Berger, P., Cannon, C. P., Fisher, L., Hasselblad, V., Foster, A., Joseph, D., Madan, M., McLendon, C., Rund, M., Tillery, N., Wood, F., Mahaffey, K. W., Irwin, C., Kulick, D., Johnson, N., Chen, J., Greenberg, S., Hogeboom, C., Lorenz, T. J., Terifay, R., Strony, J., Veltri, E. 2000; 356 (9247): 2037-2044

    Abstract

    The platelet glycoprotein IIb/IIIa inhibitors, although effective in reducing ischaemic complications of percutaneous coronary intervention, are used in few coronary stent implantation procedures. ESPRIT (Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy) is a randomised, placebo-controlled trial to assess whether a novel, double-bolus dose of eptifibatide could improve outcomes of patients undergoing coronary stenting.We recruited 2064 patients undergoing stent implantation in a native coronary artery. Immediately before percutaneous coronary intervention, patients were randomly allocated to receive eptifibatide, given as two 180 microg/kg boluses 10 min apart and a continuous infusion of 2.0 microg/kg/min for 18-24 h, or placebo, in addition to aspirin, heparin, and a thienopyridine. The primary endpoint was the composite of death, myocardial infarction, urgent target vessel revascularisation, and thrombotic bailout glycoprotein IIb/IIIa inhibitor therapy within 48 h after randomisation. The key secondary endpoint was the composite of death, myocardial infarction, or urgent target vessel revascularisation at 30 days.The trial was terminated early for efficacy. The primary endpoint was reduced from 10.5% (108 of 1024 patients on placebo [95% CI 8.7-12.4%]) to 6.6% (69 of 1040 [5.1-8.1%]) with treatment (p=0.0015). The key 30 day secondary endpoint was also reduced, from 10.5% (107 of 1024 patients on placebo [8.6-12.3%]) to 6.8% (71 of 1040 [5.3-8.4%]; p=0.0034). There was consistency in reduction of events across all components of the composite endpoint and among the major subgroups. Major bleeding was infrequent but arose more often with eptifibatide than placebo (1.3%, 13 of 1040 [0.7-2.1%]) vs 0.4%, 4 of 1024 [0.1-1.0%]; p=0.027).Routine glycoprotein IIb/IIIa inhibitor pretreatment with eptifibatide substantially reduces ischaemic complications in coronary stent intervention and is better than a strategy of reserving treatment to the bailout situation.

    View details for Web of Science ID 000165994300009

    View details for PubMedID 11145489

  • Characterization of RyR1-slow, a ryanodine receptor specific to slow-twitch skeletal muscle AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Morrissette, J., Xu, L., Nelson, A., Meissner, G., Block, B. A. 2000; 279 (5): R1889-R1898

    Abstract

    Two distinct skeletal muscle ryanodine receptors (RyR1s) are expressed in a fiber type-specific manner in fish skeletal muscle (11). In this study, we compare [(3)H]ryanodine binding and single channel activity of RyR1-slow from fish slow-twitch skeletal muscle with RyR1-fast and RyR3 isolated from fast-twitch skeletal muscle. Scatchard plots indicate that RyR1-slow has a lower affinity for [(3)H]ryanodine when compared with RyR1-fast. In single channel recordings, RyR1-slow and RyR1-fast had similar slope conductances. However, the maximum open probability (P(o)) of RyR1-slow was threefold less than the maximum P(o) of RyR1-fast. Single channel studies also revealed the presence of two populations of RyRs in tuna fast-twitch muscle (RyR1-fast and RyR3). RyR3 had the highest P(o) of all the RyR channels and displayed less inhibition at millimolar Ca(2+). The addition of 5 mM Mg-ATP or 2.5 mM beta, gamma-methyleneadenosine 5'-triphosphate (AMP-PCP) to the channels increased the P(o) and [(3)H]ryanodine binding of both RyR1s but also caused a shift in the Ca(2+) dependency curve of RyR1-slow such that Ca(2+)-dependent inactivation was attenuated. [(3)H]ryanodine binding data also showed that Mg(2+)-dependent inhibition of RyR1-slow was reduced in the presence of AMP-PCP. These results indicate differences in the physiological properties of RyRs in fish slow- and fast-twitch skeletal muscle, which may contribute to differences in the way intracellular Ca(2+) is regulated in these muscle types.

    View details for Web of Science ID 000090003700045

    View details for PubMedID 11049875

  • Cloning of a neonatal calcium atpase isoform (SERCA 1B) from extraocular muscle of adult blue marlin (Makaira nigricans) COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY Londraville, R. L., Cramer, T. D., Franck, J. P., Tullis, A., Block, B. A. 2000; 127 (2): 223-233

    Abstract

    Complete cDNAs for the fast-twitch Ca2+ -ATPase isoform (SERCA 1) were cloned and sequenced from blue marlin (Makaira nigricans) extraocular muscle (EOM). Complete cDNAs for SERCA 1 were also cloned from fast-twitch skeletal muscle of the same species. The two sequences are identical over the coding region except for the last five codons on the carboxyl end; EOM SERCA 1 cDNA codes for 996 amino acids and the fast-twitch cDNAs code for 991 aa. Phylogenetic analysis revealed that EOM SERCA 1 clusters with an isoform of Ca2+ -ATPase normally expressed in early development of mammals (SERCA 1B). This is the first report of SERCA 1B in an adult vertebrate. RNA hybridization assays indicate that 1B expression is limited to extraocular muscles. Because EOM gives rise to the thermogenic heater organ in marlin, we investigated whether SERCA 1B may play a role in heat generation, or if 1B expression is common in EOM among vertebrates. Chicken also expresses SERCA 1B in EOM, but rat expresses SERCA 1A; because SERCA 1B is not specific to heater tissue we conclude it is unlikely that it plays a specific role in intracellular heat production. Comparative sequence analysis does reveal, however, several sites that may be the source of functional differences between fish and mammalian SERCAs.

    View details for Web of Science ID 000089335000010

    View details for PubMedID 11079376

  • Structure and migration corridors in Pacific populations of the Swordfish Xiphius gladius, as inferred through analyses of mitochondrial DNA MARINE BIOLOGY Reeb, C. A., Arcangeli, L., Block, B. A. 2000; 136 (6): 1123-1131
  • Characterization of ryanodine receptor and serca isoforms from the thermogenic beater organ of marlin and swordfish. Morrissette, J. M., Franck, J., Block, B. A. BIOPHYSICAL SOCIETY. 2000: 187A
  • Orbital rete and red muscle vein anatomy indicate a high degree of endothermy in the brain and eye of the salmon shark ACTA ZOOLOGICA Tubbesing, V. A., Block, B. A. 2000; 81 (1): 49–56
  • Development of an acoustic telemetry tag for monitoring electromyograms in free-swimming fish JOURNAL OF EXPERIMENTAL BIOLOGY Dewar, H., Deffenbaugh, M., Thurmond, G., Lashkari, K., Block, B. A. 1999; 202 (19): 2693–99
  • The sarcoplasmic reticulum plays a major role in isometric contraction in atrial muscle of yellowfin tuna JOURNAL OF EXPERIMENTAL BIOLOGY Shiels, H. A., Freund, E. V., Farrell, A. P., Block, B. A. 1999; 202 (7): 881-890
  • Horizontal movements and depth distribution of large adult yellowfin tuna (Thunnus albacares) near the Hawaiian Islands, recorded using ultrasonic telemetry: implications for the physiological ecology of pelagic fishes MARINE BIOLOGY Brill, R. W., Block, B. A., Boggs, C. H., Bigelow, K. A., Freund, E. V., Marcinek, D. J. 1999; 133 (3): 395-408
  • The sarcoplasmic reticulum plays a major role in isometric contraction in atrial muscle of yellowfin tuna The Journal of experimental biology Shiels, H. A., Freund, E. V., Farrell, A. P., Block, B. A. 1999; 202 (Pt 7): 881–90

    Abstract

    We used an isometric muscle preparation to test the hypothesis that yellowfin tuna Thunnus albacares utilize the intracellular Ca2+ storage sites of the sarcoplasmic reticulum (SR) during routine contractions. Ryanodine (a blocker of SR Ca2+ release) reduced the force of contraction by approximately 50 % and the rates of contraction and relaxation by 60 % in yellowfin tuna atrium. High levels of adrenaline were unable to ameliorate the effects of ryanodine. We conclude that the SR is active in contributing Ca2+ to force development at physiological contraction frequencies. Further, we suggest that, by using intracellular Ca2+ cycling, the yellowfin tuna is able to increase the maximum contraction frequency of its cardiac muscle beyond that of most other fishes.

    View details for PubMedID 10069977

  • Development of an acoustic telemetry tag for monitoring electromyograms in free-swimming fish The Journal of experimental biology Dewar, H., Deffenbaugh, M., Thurmond, G., Lashkari, K., Block, B. A. 1999; 202 (Pt 19): 2693–99

    Abstract

    We report the development of an acoustic telemetry tag used to monitor electromyograms (EMGs) remotely from free-swimming marine fish. The device described amplifies and filters the EMG and then converts the electrical waveform into a frequency-modulated acoustic signal that is transmitted through water. The signal is then received, demodulated and recorded by the receiving system. The EMG tag described has been tested on a range of species, including toadfish Opsanus &tgr;, spiny dogfish Squalus acanthias, yellowfin tuna Thunnus albacares and eastern Pacific bonito Sarda chiliensis, in different tank environments. In certain tanks the fidelity with which the system replicates the EMG is sufficient to quantify accurately the onset, offset, duration, the integrated area under the absolute value of the signal and the number of signal zero crossings. This EMG tag will expand the scope of questions that can be addressed about the behavior and physiology of free-swimming fish.

    View details for PubMedID 10482728

  • A new satellite technology for tracking the movements of Atlantic bluefin tuna PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Block, B. A., Dewar, H., Farwell, C., Prince, E. D. 1998; 95 (16): 9384-9389

    Abstract

    The movements of Atlantic bluefin tuna (Thunnus thynnus thynnus) have captured the interest of scientists and fishers since the time of Aristotle. This tuna is unique among bony fish for maintaining elevated body temperatures (21 degrees C above ambient) and attaining large size (up to 750 kg). We describe here the use of a pop-off satellite tag, for investigating the Atlantic-wide movements and potential stock overlap of western and eastern Atlantic bluefin tuna. The tag also archives data on water temperatures. The objectives of this study were to evaluate the effectiveness of the technology, study the movements of Atlantic bluefin tuna, examine their thermal niche, and assess survivorship of tagged fish. The pop-off satellite technology provides data independent of commercial fisheries that, when deployed in sufficient quantity, should permit a critical test of the stock structure hypotheses for Atlantic bluefin tuna.

    View details for Web of Science ID 000075246600059

    View details for PubMedID 9689089

    View details for PubMedCentralID PMC21347

  • Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Franck, J. P., Morrissette, J., Keen, J. E., Londraville, R. L., Beamsley, M., Block, B. A. 1998; 275 (2): C401-C415

    Abstract

    We have cloned a group of cDNAs that encodes the skeletal ryanodine receptor isoform (RyR1) of fish from a blue marlin extraocular muscle library. The cDNAs encode a protein of 5,081 amino acids with a calculated molecular mass of 576,302 Da. The deduced amino acid sequence shows strong sequence identity to previously characterized RyR1 isoforms. An RNA probe derived from a clone of the full-length marlin RyR1 isoform hybridizes to RNA preparations from extraocular muscle and slow-twitch skeletal muscle but not to RNA preparations from fast-twitch skeletal or cardiac muscle. We have also isolated a partial RyR clone from marlin and toadfish fast-twitch muscles that shares 80% sequence identity with the corresponding region of the full-length RyR1 isoform, and a RNA probe derived from this clone hybridizes to RNA preparations from fast-twitch muscle but not to slow-twitch muscle preparations. Western blot analysis of slow-twitch muscles in fish indicates the presence of only a single high-molecular-mass RyR protein corresponding to RyR1. [3H]ryanodine binding assays revealed the fish slow-twitch muscle RyR1 had a greater sensitivity for Ca2+ than the fast-twitch muscle RyR1. The results indicate that, in fish muscle, fiber type-specific RyR1 isoforms are expressed and the two proteins are physiologically distinct.

    View details for Web of Science ID 000075174400009

    View details for PubMedID 9688594

  • Cloning and characterization of fiber type-specific ryanodine receptor isoforms in skeletal muscles of fish. American journal of physiology. Cell physiology Franck, J. P., Morrissette, J., Keen, J. E., Londraville, R. L., Beamsley, M., Block, B. A. 1998; 275 (2): C401–C415

    Abstract

    We have cloned a group of cDNAs that encodes the skeletal ryanodine receptor isoform (RyR1) of fish from a blue marlin extraocular muscle library. The cDNAs encode a protein of 5,081 amino acids with a calculated molecular mass of 576,302 Da. The deduced amino acid sequence shows strong sequence identity to previously characterized RyR1 isoforms. An RNA probe derived from a clone of the full-length marlin RyR1 isoform hybridizes to RNA preparations from extraocular muscle and slow-twitch skeletal muscle but not to RNA preparations from fast-twitch skeletal or cardiac muscle. We have also isolated a partial RyR clone from marlin and toadfish fast-twitch muscles that shares 80% sequence identity with the corresponding region of the full-length RyR1 isoform, and a RNA probe derived from this clone hybridizes to RNA preparations from fast-twitch muscle but not to slow-twitch muscle preparations. Western blot analysis of slow-twitch muscles in fish indicates the presence of only a single high-molecular-mass RyR protein corresponding to RyR1. [3H]ryanodine binding assays revealed the fish slow-twitch muscle RyR1 had a greater sensitivity for Ca2+ than the fast-twitch muscle RyR1. The results indicate that, in fish muscle, fiber type-specific RyR1 isoforms are expressed and the two proteins are physiologically distinct.

    View details for DOI 10.1152/ajpcell.1998.275.2.C401

    View details for PubMedID 29585671

  • Archival tagging of Atlantic bluefin tuna (Thunnus thynnus thynnus) MARINE TECHNOLOGY SOCIETY JOURNAL Block, B. A., Dewar, H., Williams, T., Prince, E. D., Farwell, C., Fudge, D. 1998; 32 (1): 37-46
  • Environmental preferences of yellowfin tuna (Thunnus albacares) at the northern extent of its range MARINE BIOLOGY Block, B. A., Keen, J. E., Castillo, B., Dewar, H., Freund, E. V., Marcinek, D. J., Brill, R. W., Farwell, C. 1997; 130 (1): 119-132
  • Why do tuna maintain elevated slow muscle temperatures? Power output of muscle isolated from endothermic and ectothermic fish JOURNAL OF EXPERIMENTAL BIOLOGY Altringham, J. D., Block, B. A. 1997; 200 (20): 2617–27

    Abstract

    It has been hypothesised that regional endothermy has evolved in the muscle of some tunas to enhance the locomotory performance of the fish by increasing muscle power output. Using the work loop technique, we have determined the relationship between cycle frequency and power output, over a range of temperatures, in isolated bundles of slow muscle fibres from the endothermic yellowfin tuna (Thunnus albacares) and its ectothermic relative the bonito (Sarda chiliensis). Power output in all preparations was highly temperature-dependent. A counter-current heat exchanger which could maintain a 10 degrees C temperature differential would typically double maximum muscle power output and the frequency at which maximum power is generated (fopt). The deep slow muscle of the tuna was able to operate at higher temperatures than slow muscle from the bonito, but was more sensitive to temperature change than more superficially located slow fibres from both tuna and bonito. This suggests that it has undergone some evolutionary specialisation for operation at higher, but relatively stable, temperatures. fopt of slow muscle was higher than the tailbeat frequency of undisturbed cruising tuna and, together with the high intrinsic power output of the slow muscle mass, suggests that cruising fish have a substantial slow muscle power reserve. This reserve should be sufficient to power significantly higher sustainable swimming speeds, presumably at lower energetic cost than if intrinsically less efficient fast fibres were recruited.

    View details for Web of Science ID A1997YE76900004

    View details for PubMedID 9359368

  • Effects of Ca2+ on oxidative phosphorylation in mitochondria from the thermogenic organ of marlin JOURNAL OF EXPERIMENTAL BIOLOGY OBrien, J., Block, B. A. 1996; 199 (12): 2679–87

    Abstract

    Mitochondria from the muscle-derived thermogenic (heater) organ and oxidative red muscle of the blue marlin (Makaira nigricans) were studied in order to evaluate aspects of the mechanism of thermogenesis in heater tissue. We investigated whether short-term Ca(2+)-induced uncoupling of mitochondria contributes to the thermogenic cycle of the heater organ by enhancing the respiration rate. Specific electrodes were used to obtain simultaneous measurements of oxygen consumption and Ca2+ fluxes on isolated mitochondria, and the effects of various concentrations of Ca2+ on respiration rates and the ADP phosphorylated/atomic oxygen consumed (P/O) ratio were examined. Addition of Ca2+ in excess of 10 mumol l-1 to respiring heater organ or red muscle mitochondria partially inhibited state 3 respiration and reduced the P/O ratio, indicating that the mitochondria were partially uncoupled. These effects were blocked by 2 mumol l-1 Ruthenium Red. In heater organ mitochondria, state 3 respiration rate and the P/O ratio were not significantly reduced by 1 mumol l-1 free Ca2+, a concentration likely to be near the maximum achieved in a stimulated cell. This indicates that transient increases in cytosolic Ca2+ concentration may not significantly reduce the P/O ratio of heater organ mitochondria. The activity of 2-oxoglutarate dehydrogenase in heater organ mitochondria was stimulated by approximately 15% by Ca2+ concentrations between 0.2 and 1 mumol l-1. These results suggest that heater organ mitochondria are able to maintain a normal P/O ratio and should maintain ATP output during transient increases in Ca2+ concentration, supporting a model in which an ATP-consuming process drives thermogenesis. Activation of mitochondrial dehydrogenases by low levels of Ca2+ may also enhance respiration and contribute to thermogenesis.

    View details for Web of Science ID A1996VX95400014

    View details for PubMedID 9110954

  • Expression of sarcoplasmic reticulum Ca2+-ATPase isoforms in marlin and swordfish muscle and heater cells AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY Tullis, A., Block, B. A. 1996; 271 (1): R262–R275

    Abstract

    The superior rectus muscles of marlin, swordfish, sailfish, and spearfish are modified for generating heat rather than force. This study focuses on the sarcoplasmic reticulum calcium-adenosinetriphosphatase (SR Ca(2+)-ATPase) to gain further insight into the muscle fiber type origin of the billfish "heater cell." Direct sequencing and immunolocalization demonstrated that marlin and swordfish epaxial swimming muscles express two forms of the SR Ca(2+)-ATPase in a fiber type-specific manner; red slow-twitch skeletal and cardiac muscles express the same SERCA2 message, whereas white fast-twitch skeletal muscles express a SERCA1 message. Thus the expression pattern of the SR Ca2+ pump is similar in both billfish and tetrapod muscles. Molecular and immunological studies revealed that billfish heater tissue and superior rectus muscle express both fast and slow SR Ca2+ pump isoforms. Immunohistochemical results suggest that heater cells and most extraocular muscle fibers express the fast SR Ca2+ pump. Expression of the fast SR Ca(2+)-ATPase by heater cells has implications for heater cell origin and thermogenic control.

    View details for Web of Science ID A1996UW72300033

    View details for PubMedID 8760229

  • The role of ryanodine receptor isoforms in the structure and function of the vertebrate triad 49th Annual Symposium of the Society-of-General-Physiologists on Organellar Ion Channels and Transporters Block, B. A., OBrien, J., Franck, J. ROCKEFELLER UNIV PRESS. 1996: 47–65

    View details for Web of Science ID A1996BF84C00004

    View details for PubMedID 8809933

  • PHYSIOLOGICAL DIFFERENCES BETWEEN THE ALPHA-RYANODINE AND BETA-RYANODINE RECEPTORS OF FISH SKELETAL-MUSCLE BIOPHYSICAL JOURNAL OBRIEN, J., VALDIVIA, H. H., BLOCK, B. A. 1995; 68 (2): 471–82

    Abstract

    Two isoforms of the sarcoplasmic reticulum Ca2+ release channel (ryanodine receptor or RYR) are expressed together in the skeletal muscles of most vertebrates. We have studied physiological properties of the two isoforms (alpha and beta) by comparing SR preparations from specialized fish muscles that express the alpha isoform alone to preparations from muscles containing both alpha and beta. Regulation of channel activity was assessed through [3H]ryanodine binding and reconstitution into planar lipid bilayers. Distinct differences were observed in the calcium-activation and -inactivation properties of the two isoforms. The fish alpha isoform, expressed alone in extraocular muscles, closely resembled the rabbit skeletal muscle RYR. Maximum [3H]ryanodine binding and maximum open probability (Po) of the alpha RYR were achieved from 1 to 10 microM free Ca2+. Millimolar Ca2+ reduced [3H]ryanodine binding and Po close to zero. The beta isoform more closely resembled the fish cardiac RYR in Ca2+ activation of [3H]ryanodine binding. The most prominent difference of the beta and cardiac isoforms from the alpha isoform was the lack of inactivation of [3H]ryanodine binding and Po by millimolar free Ca2+. Differences in activation of [3H]ryanodine binding by adenine nucleotides and inhibition by Mg2+ suggest that the beta and cardiac RYRs are not identical, however. [3H]ryanodine binding by the alpha RYR was selectively inhibited by 100 microM tetracaine, whereas cardiac and beta RYRs were much less affected. Tetracaine can thus be used to separate the properties of the alpha and beta RYRs in preparations in which both are present. The distinct physiological properties of the alpha and beta RYRs that are present together in most vertebrate muscles support models of EC coupling incorporating both directly coupled and Ca(2+)-coupled channels within a single triad junction.

    View details for DOI 10.1016/S0006-3495(95)80208-0

    View details for Web of Science ID A1995QC12100008

    View details for PubMedID 7696500

    View details for PubMedCentralID PMC1281711

  • CHARACTERIZATION OF THE SARCOPLASMIC-RETICULUM PROTEINS IN THE THERMOGENIC MUSCLES OF FISH JOURNAL OF CELL BIOLOGY BLOCK, B. A., OBRIEN, J., MEISSNER, G. 1994; 127 (5): 1275–87

    Abstract

    Marlins, sailfish, spearfishes, and swordfish have extraocular muscles that are modified into thermogenic organs beneath the brain. The modified muscle cells, called heater cells, lack organized myofibrils and are densely packed with sarcoplasmic reticulum (SR), transverse (T) tubules, and mitochondria. Thermogenesis in the modified extraocular muscle fibers is hypothesized to be associated with increased energy turnover due to Ca2+ cycling at the SR. In this study, the proteins associated with sequestering and releasing Ca2+ from the SR (ryanodine receptor, Ca2+ ATPase, calsequestrin) of striated muscle cells were characterized in the heater SR using immunoblot and immunofluorescent techniques. Immunoblot analysis with a monoclonal antibody that recognizes both isoforms of nonmammalian RYRs indicates that the fish heater cells express only the alpha RYR isoform. The calcium dependency of [3H]ryanodine binding to the RYR isoform expressed in heater indicates functional identity with the non-mammalian alpha RYR isoform. Fluorescent labeling demonstrates that the RYR is localized in an anastomosing network throughout the heater cell cytoplasm. Measurements of oxalate supported 45Ca2+ uptake, Ca2+ ATPase activity, and [32P]phosphoenzyme formation demonstrate that the SR contains a high capacity for Ca2+ uptake via an ATP dependent enzyme. Immunoblot analysis of calsequestrin revealed a significant amount of the Ca2+ binding protein in the heater cell SR. The present study provides the first direct evidence that the heater SR system contains the proteins necessary for Ca2+ release, re-uptake and sequestration, thus supporting the hypothesis that thermogenesis in the modified muscle cells is achieved via an ATP-dependent cycling of Ca2+ between the SR and cytosolic compartments.

    View details for DOI 10.1083/jcb.127.5.1275

    View details for Web of Science ID A1994PU78100009

    View details for PubMedID 7962089

    View details for PubMedCentralID PMC2120256

  • ENDOTHERMY IN FISHES - A PHYLOGENETIC ANALYSIS OF CONSTRAINTS, PREDISPOSITIONS, AND SELECTION PRESSURES ENVIRONMENTAL BIOLOGY OF FISHES BLOCK, B. A., FINNERTY 1994; 40 (3): 283–302

    View details for DOI 10.1007/BF00002518

    View details for Web of Science ID A1994PE95500011

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