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Barbara A Block - One of the best experts on this subject based on the ideXlab platform.
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In situ cardiac performance of Pacific Bluefin Tuna hearts in response to acute temperature change.
The Journal of experimental biology, 2020Co-Authors: Jason M Blank, Thomas D Williams, Susanna B Blackwell, Jeffery M Morrissette, Ana M Landeira-fernandez, Barbara A BlockAbstract: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.
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DISTRIBUTION OF WESTERN TAGGED ATLANTIC Bluefin Tuna DETERMINED FROM ARCHIVAL AND POP-UP SATELLITE TAGS*
2020Co-Authors: Barbara A Block, Andreas Walli, Andre Boustany, Charles J Farwell, Heidi Dewar, Eric D Prince, Tom Williams, Mike Stokesbury, Andrew C SeitzAbstract:SUMMARY The successful deployment in recent years of electronic tag technology on Atlantic Bluefin Tuna has improved our ability to examine their movements throughout the North Atlantic and Mediterranean Sea. This has rapidly improved the ability to distinguish where the Bluefin Tuna feed and breed. When biological and physical data from the tags are combined with information about sea surface temperature and ocean color from remote sensing technologies, the relationship between the movements and behaviors of the fish can be linked to oceanographic processes. This paper focuses on the results of electronic tagging of Bluefin Tuna in the western North Atlantic. RESUME
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direct measurement of swimming and diving kinematics of giant atlantic Bluefin Tuna thunnus thynnus
Royal Society Open Science, 2019Co-Authors: Steve Wilson, Robert J Schallert, Jonathan J. Dale, Adrian C Gleiss, Barbara A BlockAbstract: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.
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estimating natural mortality of atlantic Bluefin Tuna using acoustic telemetry
Scientific Reports, 2019Co-Authors: Barbara A Block, Michael J W Stokesbury, Rebecca Whitlock, Robert J Schallert, Steve Wilson, Mike Castleton, Andre BoustanyAbstract: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 0.10 yr−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.
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Hearing thresholds of swimming Pacific Bluefin Tuna Thunnus orientalis
Journal of Comparative Physiology A, 2015Co-Authors: Jonathan J. Dale, Michael D. Gray, Arthur N. Popper, Peter H. Rogers, Barbara A BlockAbstract: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.
Andre Boustany - One of the best experts on this subject based on the ideXlab platform.
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DISTRIBUTION OF WESTERN TAGGED ATLANTIC Bluefin Tuna DETERMINED FROM ARCHIVAL AND POP-UP SATELLITE TAGS*
2020Co-Authors: Barbara A Block, Andreas Walli, Andre Boustany, Charles J Farwell, Heidi Dewar, Eric D Prince, Tom Williams, Mike Stokesbury, Andrew C SeitzAbstract:SUMMARY The successful deployment in recent years of electronic tag technology on Atlantic Bluefin Tuna has improved our ability to examine their movements throughout the North Atlantic and Mediterranean Sea. This has rapidly improved the ability to distinguish where the Bluefin Tuna feed and breed. When biological and physical data from the tags are combined with information about sea surface temperature and ocean color from remote sensing technologies, the relationship between the movements and behaviors of the fish can be linked to oceanographic processes. This paper focuses on the results of electronic tagging of Bluefin Tuna in the western North Atlantic. RESUME
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estimating natural mortality of atlantic Bluefin Tuna using acoustic telemetry
Scientific Reports, 2019Co-Authors: Barbara A Block, Michael J W Stokesbury, Rebecca Whitlock, Robert J Schallert, Steve Wilson, Mike Castleton, Andre BoustanyAbstract: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 0.10 yr−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.
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east not least for pacific Bluefin Tuna
Science, 2017Co-Authors: Daniel J Madigan, Andre Boustany, Bruce B ColletteAbstract:High market values have incentivized extensive fisheries for Pacific Bluefin Tuna ( Thunnus orientalis , see the photo), a species whose longevity, commercial value, and long generation time make it particularly susceptible to overfishing ( 1 , 2 ). Today, the population of Pacific Bluefin Tuna stands at an estimated 2.6% of prefished levels ( 1 ). Yet, knowledge of its basic life history is incomplete. Recent studies ( 3 , 4 ) suggest that the fundamental distribution of Pacific Bluefin across the North Pacific has been misunderstood. The results underscore the need for basic movement ecology information to assist science-based fisheries management.
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Farming of Bluefin Tuna–Reconsidering Global Estimates and Sustainability Concerns
Reviews in Fisheries Science & Aquaculture, 2014Co-Authors: Marc Metian, Andre Boustany, Simon Pouil, Max TroellAbstract:Increased global demand for Bluefin Tuna has triggered unsustainable fishing and many wild stocks have seen dramatic declines. Improved fisheries governance is now slowly stabilizing many stocks and recently Bluefin aquaculture has emerged as an economic alternative route for supplying the market. Most of captured Bluefin Tuna directly enters the global seafood market, but an increasing part of catches are destined to aquaculture (17–37%) as Bluefin aquaculture almost exclusively depends on wild specimens for stocking. Farming is mainly being performed in the Mediterranean region, Mexico, Australia, and Japan. Few studies have focused on the global importance and future role of Bluefin aquaculture and there are confounding uncertainties related to production volumes and trends. This study provides an overview of global Bluefin Tuna aquaculture and identifies its direct and indirect interactions with wild fish stocks, outlines some of the challenges for future expansion as well as pointing out significant ...
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movements of pacific Bluefin Tuna thunnus orientalis in the eastern north pacific revealed with archival tags
Progress in Oceanography, 2010Co-Authors: Andre Boustany, Charles J Farwell, Robyn Matteson, Michael Castleton, Barbara A BlockAbstract:In this study, 253 Pacific Bluefin Tuna were archivally tagged off the coast of California, USA and Baja California, Mexico between August 2002 and August 2005. One hundred and fifty-seven fish were recaptured and 143 datasets were obtained and analyzed, yielding electronic tag datasets of up to 1203 days. Mean days at large for the 143 fish was 359 ± 248 (SD) days. A total of 38,012 geolocations were calculated from light-based longitude and SST-based latitude estimates, allowing us to examine the seasonal movement of juvenile Bluefin Tuna off the west coast of North America. Electronic tagged Bluefin Tuna showed repeatable seasonal movements along the west coast of North America. Bluefin Tuna were found farthest south in the spring when they were located off southern Baja California, Mexico and farthest north in the fall when fish were found predominately off central and northern California. Fish showed latitudinal movement patterns that were correlated with peaks in coastal upwelling-induced primary productivity. Interannual variation in the locality of these productivity peaks was linked with a corresponding movement in the distribution of tagged fish. Overall geographical area occupied by tagged Bluefin varied with primary productivity, with fish being more tightly clustered in areas of high productivity and more dispersed in regions of low productivity. In the spring through fall, Bluefin Tuna were located in areas with the highest levels of primary productivity available in the California Current ecosystem. However, in the winter months, tagged Bluefin Tuna were found in areas with lower productivity compared to other regions along the coast at that time of year suggesting that during the winter, Bluefin Tuna are feeding on aggregations of pelagic red crabs, sardines and anchovies that preferentially spawn in areas of reduced coastal upwelling.
Charles J Farwell - One of the best experts on this subject based on the ideXlab platform.
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DISTRIBUTION OF WESTERN TAGGED ATLANTIC Bluefin Tuna DETERMINED FROM ARCHIVAL AND POP-UP SATELLITE TAGS*
2020Co-Authors: Barbara A Block, Andreas Walli, Andre Boustany, Charles J Farwell, Heidi Dewar, Eric D Prince, Tom Williams, Mike Stokesbury, Andrew C SeitzAbstract:SUMMARY The successful deployment in recent years of electronic tag technology on Atlantic Bluefin Tuna has improved our ability to examine their movements throughout the North Atlantic and Mediterranean Sea. This has rapidly improved the ability to distinguish where the Bluefin Tuna feed and breed. When biological and physical data from the tags are combined with information about sea surface temperature and ocean color from remote sensing technologies, the relationship between the movements and behaviors of the fish can be linked to oceanographic processes. This paper focuses on the results of electronic tagging of Bluefin Tuna in the western North Atlantic. RESUME
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movements of pacific Bluefin Tuna thunnus orientalis in the eastern north pacific revealed with archival tags
Progress in Oceanography, 2010Co-Authors: Andre Boustany, Charles J Farwell, Robyn Matteson, Michael Castleton, Barbara A BlockAbstract:In this study, 253 Pacific Bluefin Tuna were archivally tagged off the coast of California, USA and Baja California, Mexico between August 2002 and August 2005. One hundred and fifty-seven fish were recaptured and 143 datasets were obtained and analyzed, yielding electronic tag datasets of up to 1203 days. Mean days at large for the 143 fish was 359 ± 248 (SD) days. A total of 38,012 geolocations were calculated from light-based longitude and SST-based latitude estimates, allowing us to examine the seasonal movement of juvenile Bluefin Tuna off the west coast of North America. Electronic tagged Bluefin Tuna showed repeatable seasonal movements along the west coast of North America. Bluefin Tuna were found farthest south in the spring when they were located off southern Baja California, Mexico and farthest north in the fall when fish were found predominately off central and northern California. Fish showed latitudinal movement patterns that were correlated with peaks in coastal upwelling-induced primary productivity. Interannual variation in the locality of these productivity peaks was linked with a corresponding movement in the distribution of tagged fish. Overall geographical area occupied by tagged Bluefin varied with primary productivity, with fish being more tightly clustered in areas of high productivity and more dispersed in regions of low productivity. In the spring through fall, Bluefin Tuna were located in areas with the highest levels of primary productivity available in the California Current ecosystem. However, in the winter months, tagged Bluefin Tuna were found in areas with lower productivity compared to other regions along the coast at that time of year suggesting that during the winter, Bluefin Tuna are feeding on aggregations of pelagic red crabs, sardines and anchovies that preferentially spawn in areas of reduced coastal upwelling.
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annual migrations diving behavior and thermal biology of atlantic Bluefin Tuna thunnus thynnus on their gulf of mexico breeding grounds
Marine Biology, 2007Co-Authors: Steven L H Teo, Michael J W Stokesbury, Charles J Farwell, Kevin C Weng, Heidi Dewar, Eric D Prince, Andrew C Seitz, Andre M Boustany, Shana Beemer, Barbara A BlockAbstract:Electronic tags were used to examine the biology of Atlantic Bluefin Tuna (Thunnus thynnus L.) on their breeding grounds in the Gulf of Mexico (GOM). The hypothesis that movement patterns, div- ing behavior, and thermal biology change during dif- ferent stages of the breeding migration was tested. Mature Atlantic Bluefin Tuna tagged in the western Atlantic and the GOM, were on their breeding grounds from February to June for an average of 39 ± 11 days. The Bluefin Tuna experienced significantly warmer mean sea surface temperatures (SSTs) within the GOM (26.4 ± 1.6� C) than outside the GOM (20.2 ± 1.9� C). As the Bluefin Tuna entered and exited the GOM, the fish dove to daily maximum depths of 568 ± 50 and 580 ± 144 m, respectively, and exhibited directed movement paths to and from the localized breeding areas. During the putative breeding phase, the Bluefin Tuna had significantly shallower daily max- imum depths (203 ± 76 m), and exhibited shallow oscillatory dives during the night. The movement paths of the Bluefin Tuna during the breeding phase were significantly more residential and sinuous. The heat transfer coefficients (K) were calculated for a Bluefin Tuna in the GOM using the recorded ambient and body temperatures. The K for this fish increased rapidly at the high ambient temperatures encountered in the GOM, and was significantly higher at night in the breeding phase when the fish was exhibiting shallow oscillatory dives. This suggests that the fish were behaviorally and physiologically thermoregulating in the Gulf of Mexico. This study demonstrates that the movement patterns, diving behavior, and thermal biology of Atlantic Bluefin Tuna change significantly at different stages of the breeding migration and can be used to define spawning location and timing.
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electronic tagging and population structure of atlantic Bluefin Tuna
Nature, 2005Co-Authors: Barbara A Block, Andreas Walli, Andre Boustany, Michael J W Stokesbury, Charles J Farwell, Kevin C Weng, Heidi Dewar, Thomas D WilliamsAbstract:The Atlantic Bluefin Tuna is at the centre of an international debate in fisheries conservation. Last summer the western Atlantic Bluefin Tuna fishery collapsed and some conservationists say it will not recover unless the International Commission for Conservation of Atlantic Tunas adopts a tougher regime. Results from an electronic tagging programme on Bluefin Tuna are presented this week, and they make alarming reading. Western tagged Bluefin Tuna are shown to migrate freely across the international stock boundary into the eastern Atlantic, where they are vulnerable to European fisheries; and both known spawning grounds, in the Gulf of Mexico and the Mediterranean Sea, are shown to be linked to the endangered western Atlantic fishery. Electronic tags that archive or transmit stored data to satellites have advanced the mapping of habitats used by highly migratory fish in pelagic ecosystems1,2,3,4,5,6. 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 data7,8,9 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.
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MIGRATORY MOVEMENTS OF PACIFIC Bluefin Tuna OFF CALIFORNIA
California Sea Grant College Program, 2005Co-Authors: Barbara A Block, Charles J FarwellAbstract:Author(s): Block, Barbara A.; Farwell, Charles J. | Abstract: The genus Thunnus of the family Scombridae includes three species of Bluefin Tunas (Atlantic Bluefin Tuna – T. thynnus, Pacific Bluefin Tuna - T. orientalis and southern Bluefin Tuna - T. maccoyii). The Bluefin Tunas were first recognized as two independent species (Northern and Southern Bluefin) based on subtle differences in morphological characters. Northern Bluefin Tunas are now recognized as morphologically, geographically and genetically separate species located in the Atlantic and Pacific oceans.The Pacific Bluefin (T. orientalis) is the only species which remains unmanaged; this lack of management persists despite intensive fisheries on both sides of the Pacific. The current life history model indicates that these fish spawn in the western Pacific (Sea of Japan, Philippine Sea and East China Sea). Either late in the first year or early in the second year, a portion of the population migrates to the western coast of the United States and Mexico, a journey of over 8700 km (Bayliff et al., 1991). The young fish that have migrated into the eastern Pacific are thought to remain there for several years, feeding on sardines and anchovies in regions of intense upwelling (Bayliff et al., 1991, Bayliff, 1993). While these Tuna are fished only seasonally off California and Mexico, they may be a year-round resident (Bayliff, 1991). The migrants then travel back to the western Pacific to spawn. Why some Bluefin remain in the western Pacific while others migrate across the ocean basin is unresolved. How long they stay in the eastern Pacific, what habitats are most important, what triggers their return to the west is unclear.
Molly E. Lutcavage - One of the best experts on this subject based on the ideXlab platform.
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Inclusion of prey data improves prediction of Bluefin Tuna (Thunnus thynnus) distribution
Fisheries Oceanography, 2020Co-Authors: Robert S. Schick, Molly E. LutcavageAbstract:We examined the distribution of Atlantic Bluefin Tuna (Thunnus thynnus) in the Gulf of Maine, Northwest Atlantic Ocean, from 17 to 23 August 1995, in relation to physical and biological parameters. Specifically, we fit a binomial GLM to the Bluefin Tuna presence–absence data and predictor variables that include: sea surface temperature (SST), ocean depth, distance to an SST front, time-lagged density of SST fronts, and an interpolated surface of Atlantic herring (Clupea harengus) density. In addition, we use simple and partial Mantel tests to examine whether Bluefin Tuna presence–absence data are significantly associated with these predictors, once spatial autocorrelation is accounted for. Results suggest that the distribution of Bluefin Tuna significantly correlated with herring density (z = 3.525, P = 0.000424), and that inclusion of biological variables results in a more parsimonious model. Mantel tests results indicate that Bluefin Tuna abundance is significantly correlated with herring density after the effect of spatial structure is removed (Mantel r = 0.043, P
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Decline in condition of northern Bluefin Tuna (Thunnus thynnus) in the Gulf of Maine
2020Co-Authors: Walter J. Golet, Andrew B. Cooper, Robert Campbell, Molly E. LutcavageAbstract:The northern Bluefin Tuna (Thunnus thynnus) is a highly mobile apex predator in the Gulf of Maine. Despite current stock assessments that indicate historically high abundance of its main prey, Atlantic herring (Clupea harengus), commercial fishermen have observed declines in the somatic condition of northern Bluefin Tuna during the last decade. We examined this claim by reviewing detailed logbooks of northern Bluefin Tuna condition from a local fishermen’s cooperative and applying multinomial regression, a robust tool for exploring how a categorical variable may be related to other variables of interest. The data set contained >3082 observations of condition (fat and oil content and fish shape) from fish landed between 1991 and 2004. Energy from stored lipids is used for migration and reproduction; therefore a reduction in energy acquisition on Bluefin Tuna feeding grounds could diminish allocations to growth and gamete production and have detrimental consequences for rebuilding the western Atlantic population. A decline in northern Bluefin Tuna somatic condition could indicate substantial changes in the bottom-up transfer of energy in the Gulf of Maine, shifts in their reproductive or migratory patterns, impacts of fishing pressure, or synergistic effects from multiple causes.
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ON-GOING Bluefin Tuna RESEARCH IN THE BAY OF BISCAY (NORTHEAST ATLANTIC): THE "HEGALABUR 2009" PROJECT
2020Co-Authors: Nicolas Goñi, Benjamin Galuardi, Molly E. Lutcavage, Igaratza Fraile, Igor Arregui, Josu Santiago, Guillermo Boyra, Xabier Irigoien, John M. Logan, Andone EstonbaAbstract:Little research has been focused to date on the juvenile fraction of Atlantic Bluefin Tuna (Thunnus thynnus, BFT) populations. For instance, although the baitboat CPUE from the Bay of Biscay is used as the only recruitment index for the eastern stock, little is known about the role of this juvenile feeding area within the life cycle of Bluefin Tuna. This, together with recent changes in the Bluefin Tuna management context, might jeopardize the usefulness of the CPUEderived index. One objective of the ongoing “Hegalabur 2009” project is to analyze the possibility of using acoustic technologies (long-range sonar and ecoshounder) to get abundance indices of Bluefin Tuna in the Bay of Biscay. On the other hand, the project aims to understand the role of the Bay of Biscay in the life cycle of BFT, by identifying the origin of the Bluefin Tuna present in the Bay of Biscay, and the variability of the proportion of individuals of different origins. Acoustic surveys (scientific echosounders and commercial sonars), biological sampling and tagging (conventional and electronic) have been conducted. Some posibilities for developing acoustic indices of abundance are discussed, as well as the perspectives for different analyses (genetics, otolith microchemistry, reproduction, tagging).
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discovery of a spawning ground reveals diverse migration strategies in atlantic Bluefin Tuna thunnus thynnus
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: David E Richardson, Katrin E Marancik, Jeffrey Robert Guyon, Benjamin Galuardi, Harvey J Walsh, Sharon Wildes, Douglas A Yates, Molly E. Lutcavage, Jonathan A HareAbstract:Atlantic Bluefin Tuna are a symbol of both the conflict between preservationist and utilitarian views of top ocean predators, and the struggle to reach international consensus on the management of migratory species. Currently, Atlantic Bluefin Tuna are managed as an early-maturing eastern stock, which spawns in the Mediterranean Sea, and a late-maturing western stock, which spawns in the Gulf of Mexico. However, electronic tagging studies show that many Bluefin Tuna, assumed to be of a mature size, do not visit either spawning ground during the spawning season. Whether these fish are spawning in an alternate location, skip-spawning, or not spawning until an older age affects how vulnerable this species is to anthropogenic stressors including exploitation. We use larval collections to demonstrate a Bluefin Tuna spawning ground in the Slope Sea, between the Gulf Stream and northeast United States continental shelf. We contend that western Atlantic Bluefin Tuna have a differential spawning migration, with larger individuals spawning in the Gulf of Mexico, and smaller individuals spawning in the Slope Sea. The current life history model, which assumes only Gulf of Mexico spawning, overestimates age at maturity for the western stock. Furthermore, individual Tuna occupy both the Slope Sea and Mediterranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete spawning-site fidelity. Overall, this complexity of spawning migrations questions whether there is complete independence in the dynamics of eastern and western Atlantic Bluefin Tuna and leads to lower estimates of the vulnerability of this species to exploitation and other anthropogenic stressors.
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The paradox of the pelagics: why Bluefin Tuna can go hungry in a sea of plenty
Marine Ecology Progress Series, 2015Co-Authors: Walter J. Golet, Benjamin Galuardi, Molly E. Lutcavage, Andrew B. Cooper, Nicholas R. Record, Sigrid Lehuta, Andrew J. PershingAbstract:ABSTRACT: Large marine predators such as Tunas and sharks play an important role in structuringmarine food webs. Their future populations depend on the environmental conditions they en -counter across life history stages and the level of human exploitation. Standard predator−prey rela-tionships suggest favorable conditions (high prey abundance) should result in successful foragingand reproductive output. Here, we demonstrate that these assumptions are not invariably validacross species, and that somatic condition of Atlantic Bluefin Tuna Thunnus thynnus in the Gulf ofMaine declined in the presence of high prey abundance. We show that the paradox of decliningBluefin Tuna condition during a period of high prey abundance is explained by a change in the sizestructure of their prey. Specifically, we identified strong correlations between Bluefin Tuna bodycondition, the relative abundance of large Atlantic herring Clupea harengus , and the energeticpayoff resulting from consuming different sizes of herring. This correlation is consistent withoptimal foraging theory, explaining why Bluefin Tuna condition suffers even when prey is abundant.Furthermore, optimal foraging principles explain a shift in traditional Bluefin Tuna foraging areas,toward regions with a higher proportion of large herring. Bluefin Tuna appear sensitive to changesin the size spectrum of prey rather than prey abundance, impacting their distribution, reproductionand economic value. Fisheries managers will now face the challenge of how to manage for highabundance of small pelagic fish, which benefits benthic fishes and mammalian predators, andmaintain a robust size structure beneficial for top predators with alternative foraging strategies.KEY WORDS: Bluefin Tuna · Herring · Optimal foraging · Condition ·
Michael J W Stokesbury - One of the best experts on this subject based on the ideXlab platform.
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estimating natural mortality of atlantic Bluefin Tuna using acoustic telemetry
Scientific Reports, 2019Co-Authors: Barbara A Block, Michael J W Stokesbury, Rebecca Whitlock, Robert J Schallert, Steve Wilson, Mike Castleton, Andre BoustanyAbstract: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 0.10 yr−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.
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Estimating mortality of Atlantic Bluefin Tuna (Thunnus thynnus) in an experimental recreational catch-and-release fishery
Biological Conservation, 2011Co-Authors: Michael J W Stokesbury, John D. Neilson, Edward Susko, Steven J. CookeAbstract:Abstract The abundance of Atlantic Bluefin Tuna has been severely reduced since the advent of industrial fishing. A recreational catch-and-release fishery is currently being developed to target Bluefin Tuna in the southern Gulf of St. Lawrence, off the coast of Prince Edward Island, Canada. To evaluate the sustainability of this fishery, it is necessary to quantify post-release mortality for use in management models. Using pop-up archival satellite tags, we estimated the post-release mortality rate of Bluefin Tuna captured and released in an experimental recreational fishery. Fish were captured using bait on circle hooks and all fish were hooked in the jaw. Fish were released without being brought onboard the boat. Tags reported from 2 to 246 days post release. Two of 59 Bluefin Tuna died after catch-and-release yielding a mortality rate of 3.4% (95% C.I. = 0.8%
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annual migrations diving behavior and thermal biology of atlantic Bluefin Tuna thunnus thynnus on their gulf of mexico breeding grounds
Marine Biology, 2007Co-Authors: Steven L H Teo, Michael J W Stokesbury, Charles J Farwell, Kevin C Weng, Heidi Dewar, Eric D Prince, Andrew C Seitz, Andre M Boustany, Shana Beemer, Barbara A BlockAbstract:Electronic tags were used to examine the biology of Atlantic Bluefin Tuna (Thunnus thynnus L.) on their breeding grounds in the Gulf of Mexico (GOM). The hypothesis that movement patterns, div- ing behavior, and thermal biology change during dif- ferent stages of the breeding migration was tested. Mature Atlantic Bluefin Tuna tagged in the western Atlantic and the GOM, were on their breeding grounds from February to June for an average of 39 ± 11 days. The Bluefin Tuna experienced significantly warmer mean sea surface temperatures (SSTs) within the GOM (26.4 ± 1.6� C) than outside the GOM (20.2 ± 1.9� C). As the Bluefin Tuna entered and exited the GOM, the fish dove to daily maximum depths of 568 ± 50 and 580 ± 144 m, respectively, and exhibited directed movement paths to and from the localized breeding areas. During the putative breeding phase, the Bluefin Tuna had significantly shallower daily max- imum depths (203 ± 76 m), and exhibited shallow oscillatory dives during the night. The movement paths of the Bluefin Tuna during the breeding phase were significantly more residential and sinuous. The heat transfer coefficients (K) were calculated for a Bluefin Tuna in the GOM using the recorded ambient and body temperatures. The K for this fish increased rapidly at the high ambient temperatures encountered in the GOM, and was significantly higher at night in the breeding phase when the fish was exhibiting shallow oscillatory dives. This suggests that the fish were behaviorally and physiologically thermoregulating in the Gulf of Mexico. This study demonstrates that the movement patterns, diving behavior, and thermal biology of Atlantic Bluefin Tuna change significantly at different stages of the breeding migration and can be used to define spawning location and timing.
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electronic tagging and population structure of atlantic Bluefin Tuna
Nature, 2005Co-Authors: Barbara A Block, Andreas Walli, Andre Boustany, Michael J W Stokesbury, Charles J Farwell, Kevin C Weng, Heidi Dewar, Thomas D WilliamsAbstract:The Atlantic Bluefin Tuna is at the centre of an international debate in fisheries conservation. Last summer the western Atlantic Bluefin Tuna fishery collapsed and some conservationists say it will not recover unless the International Commission for Conservation of Atlantic Tunas adopts a tougher regime. Results from an electronic tagging programme on Bluefin Tuna are presented this week, and they make alarming reading. Western tagged Bluefin Tuna are shown to migrate freely across the international stock boundary into the eastern Atlantic, where they are vulnerable to European fisheries; and both known spawning grounds, in the Gulf of Mexico and the Mediterranean Sea, are shown to be linked to the endangered western Atlantic fishery. Electronic tags that archive or transmit stored data to satellites have advanced the mapping of habitats used by highly migratory fish in pelagic ecosystems1,2,3,4,5,6. 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 data7,8,9 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.