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Barbara A Block - One of the best experts on this subject based on the ideXlab platform.
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stock of origin catch estimation of Atlantic Bluefin Tuna thunnus thynnus based on observed spatial distributions
Canadian Journal of Fisheries and Aquatic Sciences, 2021Co-Authors: Emilius A Aalto, Robert J Schallert, Michael J. W. Stokesbury, Francesco Ferretti, Matthew V Lauretta, John F Walter, Barbara A BlockAbstract:Atlantic Bluefin Tuna (Thunnus thynnus) are a large, highly migratory fish distributed throughout the North Atlantic Ocean and adjacent seas currently managed as two discrete stocks: western and ea...
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direct measurement of swimming and diving kinematics of giant Atlantic Bluefin Tuna thunnus thynnus
Royal Society Open Science, 2019Co-Authors: Robert J Schallert, Adrian C Gleiss, Jonathan J Dale, Steve Wilson, 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, Rebecca Whitlock, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Steve Wilson, 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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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, 2015Co-Authors: Steven G Wilson, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Andre Boustany, Ian D Jonsen, James E Ganong, Aaron D Spares, Barbara A BlockAbstract:The objective of this study was to advance the use of pop-up satellite archival tags to track the migrations of Atlantic Bluefin Tuna (Thunnus thynnus) to their spawning grounds. Deployment of tags occurred in the Gulf of St. Lawrence, Canada, during fall months from 2007 to 2013. Pop-up satellite archival tags (n = 135) were attached to 125 Atlantic Bluefin Tuna (curved fork length (CFL) = 268 ± 20 cm (mean ± SD)) with the objective of keeping tags on until visitation to a spawning area or longer. A dataset of 18 800 days was acquired, which included 5800 days of time-series data from 19 recovered satellite tags. Many Atlantic Bluefin Tuna visited the Gulf of Mexico spawning grounds (74%), the mean size of which was 275 ± 14 cm (CFL ± SD, n = 49), with a measured CFL of 243 to 302 cm. These fish had a mean entry date into the Gulf of Mexico of 14 January ± 42 days (SD). The mean residency period for fish that had tracks with entrance and exit from the Gulf of Mexico was 123 ± 49 days (SD) (n = 22). Atlan...
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seasonal movements aggregations and diving behavior of Atlantic Bluefin Tuna thunnus thynnus revealed with archival tags
2013Co-Authors: Andreas Walli, Steven L H Teo, Charles J. Farwell, Eric D Prince, Andre Boustany, Heidi Dewar, Tom Williams, Barbara A BlockAbstract: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 (167633 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.
Molly E. Lutcavage - One of the best experts on this subject based on the ideXlab platform.
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reply to safina and walter et al multiple lines of evidence for size structured spawning migrations in western Atlantic Bluefin Tuna
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: David E. Richardson, Katrin E Marancik, Jeffrey Robert Guyon, Harvey J Walsh, Sharon Wildes, Douglas A Yates, Molly E. Lutcavage, Benjamin Galuardi, Jonathan A HareAbstract:Walter et al. (1) and Safina (2) raise numerous concerns regarding our study (3). Specifically, they question our conclusions that (i) a majority of spawning occurs outside the Gulf of Mexico, (ii) western North Atlantic Bluefin Tuna mature earlier than currently estimated, and (iii) additional spawning locations and younger age at maturity mean that the western Atlantic Bluefin Tuna are less vulnerable to anthropogenic impacts, including exploitation.
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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, Harvey J Walsh, Sharon Wildes, Douglas A Yates, Molly E. Lutcavage, Benjamin Galuardi, 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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single nucleotide polymorphism discovery in albacore and Atlantic Bluefin Tuna provides insights into worldwide population structure
Animal Genetics, 2013Co-Authors: Aitor Albaina, Molly E. Lutcavage, Haritz Arrizabalaga, Mikel Iriondo, I Velado, Urtzi Laconcha, Iratxe Zarraonaindia, M A Pardo, W S Grant, Andone EstonbaAbstract:Summary The optimal management of the commercially important, but mostly over-exploited, pelagic Tunas, albacore (Thunnus alalunga Bonn., 1788) and Atlantic Bluefin Tuna (BFT; Thunnus thynnus L., 1758), requires a better understanding of population structure than has been provided by previous molecular methods. Despite numerous studies of both species, their population structures remain controversial. This study reports the development of single nucleotide polymorphisms (SNPs) in albacore and BFT and the application of these SNPs to survey genetic variability across the geographic ranges of these Tunas. A total of 616 SNPs werediscoveredin35albacoreTunabycomparingsequencesof54nuclearDNAfragments.A panel of 53 SNPs yielded FST values ranging from 0.0 to 0.050 between samples after genotyping 460 albacore collected throughout the distribution of this species. No significant heterogeneity was detected within oceans, but between-ocean comparisons (Atlantic, Pacific and Indian oceans along with Mediterranean Sea) were significant. Additionally, a 17-SNP panel was developed in Atlantic BFT by cross-species amplification in 107 fish. This limited number of SNPs discriminated between samples from the two major spawning areas of Atlantic BFT (FST = 0.116). The SNP markers developed in this study can be used to genotype large numbers of fish without the need for standardizing alleles among laboratories.
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dispersal routes and habitat utilization of juvenile Atlantic Bluefin Tuna thunnus thynnus tracked with mini psat and archival tags
PLOS ONE, 2012Co-Authors: Benjamin Galuardi, Molly E. LutcavageAbstract:Between 2005 and 2009, we deployed 58 miniature pop-up satellite archival tags (PSAT) and 132 implanted archival tags on juvenile Atlantic Bluefin Tuna (age 2–5) in the northwest Atlantic Ocean. Data returned from these efforts (n = 26 PSATs, 1 archival tag) revealed their dispersal routes, horizontal and vertical movements and habitat utilization. All of the tagged Bluefin Tuna remained in the northwest Atlantic for the duration observed, and in summer months exhibited core-use of coastal seas extending from Maryland to Cape Cod, MA, (USA) out to the shelf break. Their winter distributions were more spatially disaggregated, ranging south to the South Atlantic Bight, northern Bahamas and Gulf Stream. Vertical habitat patterns showed that juvenile Bluefin Tuna mainly occupied shallow depths (mean = 5–12 m, sd = 15–23.7 m) and relatively warm water masses in summer (mean = 17.9–20.9°C, sd = 4.2–2.6°C) and had deeper and more variable depth patterns in winter (mean = 41–58 m, sd = 48.9–62.2 m). Our tagging results reveal annual dispersal patterns, behavior and oceanographic associations of juvenile Atlantic Bluefin Tuna that were only surmised in earlier studies. Fishery independent profiling from electronic tagging also provide spatially and temporally explicit information for evaluating dispersals rates, population structure and fisheries catch patterns.
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diet of young Atlantic Bluefin Tuna thunnus thynnus in eastern and western Atlantic foraging grounds
Marine Biology, 2011Co-Authors: John M Logan, Walter J. Golet, Nicolas Goñi, Molly E. Lutcavage, Silvia Barreiro, E Rodriguezmarin, Haritz ArrizabalagaAbstract:Atlantic Bluefin Tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades. Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved fork length) Bluefin Tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic Ocean. In the Mid-Atlantic Bight, Bluefin Tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed that juvenile Bluefin Tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed <10% of the prey weights based upon traditional stomach content analyses. Trophic position was similar to juvenile fish sampled in the NW Atlantic but lower than juveniles sampled in the Mediterranean Sea in previous studies. Our findings indicate that juvenile Bluefin Tuna targeted a relatively small range of prey species and regional foraging patterns remained consistent over time in the Mid-Atlantic Bight but changed in relation to local prey availability in the Bay of Biscay.
Benjamin Galuardi - One of the best experts on this subject based on the ideXlab platform.
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reply to safina and walter et al multiple lines of evidence for size structured spawning migrations in western Atlantic Bluefin Tuna
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: David E. Richardson, Katrin E Marancik, Jeffrey Robert Guyon, Harvey J Walsh, Sharon Wildes, Douglas A Yates, Molly E. Lutcavage, Benjamin Galuardi, Jonathan A HareAbstract:Walter et al. (1) and Safina (2) raise numerous concerns regarding our study (3). Specifically, they question our conclusions that (i) a majority of spawning occurs outside the Gulf of Mexico, (ii) western North Atlantic Bluefin Tuna mature earlier than currently estimated, and (iii) additional spawning locations and younger age at maturity mean that the western Atlantic Bluefin Tuna are less vulnerable to anthropogenic impacts, including exploitation.
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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, Harvey J Walsh, Sharon Wildes, Douglas A Yates, Molly E. Lutcavage, Benjamin Galuardi, 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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dispersal routes and habitat utilization of juvenile Atlantic Bluefin Tuna thunnus thynnus tracked with mini psat and archival tags
PLOS ONE, 2012Co-Authors: Benjamin Galuardi, Molly E. LutcavageAbstract:Between 2005 and 2009, we deployed 58 miniature pop-up satellite archival tags (PSAT) and 132 implanted archival tags on juvenile Atlantic Bluefin Tuna (age 2–5) in the northwest Atlantic Ocean. Data returned from these efforts (n = 26 PSATs, 1 archival tag) revealed their dispersal routes, horizontal and vertical movements and habitat utilization. All of the tagged Bluefin Tuna remained in the northwest Atlantic for the duration observed, and in summer months exhibited core-use of coastal seas extending from Maryland to Cape Cod, MA, (USA) out to the shelf break. Their winter distributions were more spatially disaggregated, ranging south to the South Atlantic Bight, northern Bahamas and Gulf Stream. Vertical habitat patterns showed that juvenile Bluefin Tuna mainly occupied shallow depths (mean = 5–12 m, sd = 15–23.7 m) and relatively warm water masses in summer (mean = 17.9–20.9°C, sd = 4.2–2.6°C) and had deeper and more variable depth patterns in winter (mean = 41–58 m, sd = 48.9–62.2 m). Our tagging results reveal annual dispersal patterns, behavior and oceanographic associations of juvenile Atlantic Bluefin Tuna that were only surmised in earlier studies. Fishery independent profiling from electronic tagging also provide spatially and temporally explicit information for evaluating dispersals rates, population structure and fisheries catch patterns.
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complex migration routes of Atlantic Bluefin Tuna thunnus thynnus question current population structure paradigm
Canadian Journal of Fisheries and Aquatic Sciences, 2010Co-Authors: Walter J. Golet, Benjamin Galuardi, Francois Royer, John Loganj Logan, John Neilsonj NeilsonAbstract:Movements of Atlantic Bluefin Tuna (Thunnus thynnus, ABFT) from specific western Atlantic forage grounds are not well described, and the extent of their spawning areas is mainly surmised. In 2005 a...
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complex migration routes of Atlantic Bluefin Tuna thunnus thynnus question current population structure paradigm
Canadian Journal of Fisheries and Aquatic Sciences, 2010Co-Authors: Walter J. Golet, Benjamin Galuardi, Francois Royer, John Loganj Logan, John Neilsonj NeilsonAbstract:Movements of Atlantic Bluefin Tuna (Thunnus thynnus, ABFT) from specific western Atlantic forage grounds are not well described, and the extent of their spawning areas is mainly surmised. In 2005 and 2006, we deployed 41 pop-up satellite archival tags (PSATs) on adult Atlantic Bluefin Tuna off the coast of Nova Scotia, Canada, and on Georges Bank. During the assumed spawning period, 56% of the tagged ABFT occupied a known spawning area, while 44% were located in distant oceanic regions. Assuming obligate annual spawning, these results are inconsistent with the notion of spawning site fidelity to the Gulf of Mexico. The ocean-wide migrations of adult ABFT tagged on a common forage ground suggest evidence of a metapopulation requiring more spatially explicit management than the current simple two-stock structure.
Andre Boustany - 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, Rebecca Whitlock, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Steve Wilson, 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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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, 2015Co-Authors: Steven G Wilson, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Andre Boustany, Ian D Jonsen, James E Ganong, Aaron D Spares, Barbara A BlockAbstract:The objective of this study was to advance the use of pop-up satellite archival tags to track the migrations of Atlantic Bluefin Tuna (Thunnus thynnus) to their spawning grounds. Deployment of tags occurred in the Gulf of St. Lawrence, Canada, during fall months from 2007 to 2013. Pop-up satellite archival tags (n = 135) were attached to 125 Atlantic Bluefin Tuna (curved fork length (CFL) = 268 ± 20 cm (mean ± SD)) with the objective of keeping tags on until visitation to a spawning area or longer. A dataset of 18 800 days was acquired, which included 5800 days of time-series data from 19 recovered satellite tags. Many Atlantic Bluefin Tuna visited the Gulf of Mexico spawning grounds (74%), the mean size of which was 275 ± 14 cm (CFL ± SD, n = 49), with a measured CFL of 243 to 302 cm. These fish had a mean entry date into the Gulf of Mexico of 14 January ± 42 days (SD). The mean residency period for fish that had tracks with entrance and exit from the Gulf of Mexico was 123 ± 49 days (SD) (n = 22). Atlan...
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seasonal movements aggregations and diving behavior of Atlantic Bluefin Tuna thunnus thynnus revealed with archival tags
2013Co-Authors: Andreas Walli, Steven L H Teo, Charles J. Farwell, Eric D Prince, Andre Boustany, Heidi Dewar, Tom Williams, Barbara A BlockAbstract: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 (167633 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.
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Mitochondrial DNA and electronic tracking reveal population structure of Atlantic Bluefin Tuna (Thunnus thynnus)
Marine Biology, 2008Co-Authors: Andre Boustany, Carol A. Reeb, Barbara A BlockAbstract:Population subdivision was examined in Atlantic Bluefin Tuna ( Thunnus thynnus ) through sequencing of the control region of the mitochondrial genome. A total of 178 samples from the spawning grounds in the Gulf of Mexico, Bahamas and Mediterranean Sea were analyzed. Among the samples from these locations were 36 electronically tagged Bluefin Tuna that were tagged in the North Atlantic and subsequently traveled to one of these known spawning grounds during the spawning season. Bluefin Tuna populations from the Gulf of Mexico and the Mediterranean Sea were found to be genetically distinct based on Φ_st, and sequence nearest neighbor analyses, showing that these two major spawning areas support independent stocks. Sequence nearest neighbor analysis indicated significant population subdivision among the Gulf of Mexico, western Mediterranean and eastern Mediterranean Sea. However, it was not possible to find significant pairwise differences between any sampling areas when using all samples. If only samples that had a high likelihood of assignment to a specific spawning site were used (young of the year, spawning adults), the differentiation increased among all sampling areas and the Western Mediterranean Sea was distinct from the Eastern Mediterranean Sea and the Gulf of Mexico. It was not possible to distinguish samples from the Bahamas from those collected at any of the other sampling sites. These data support tagging results that suggested distinctness of the Gulf of Mexico, Eastern and Western Mediterranean Sea spawning areas. This level of stock differentiation is only possible if Atlantic Bluefin Tuna show strong natal homing to individual spawning grounds.
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oceanographic preferences of Atlantic Bluefin Tuna thunnus thynnus on their gulf of mexico breeding grounds
Marine Biology, 2007Co-Authors: Andre Boustany, Barbara A BlockAbstract:Electronic tagging and remotely sensed oceanographic data were used to determine the oceanographic habitat use and preferences of Atlantic Bluefin Tuna (Thunnus thynnus L.) exhibiting behaviors associated with breeding in the Gulf of Mexico (GOM). Oceanographic habitats used by 28 Atlantic Bluefin Tuna exhibiting breeding behavior (259 days) were compared with available habitats in the GOM, using Monte Carlo tests and discrete choice models. Habitat utilization and preference patterns for ten environmental parameters were quantified: bathymetry, bathymetric gradient, SST, SST gradient, surface chlorophyll concentration, surface chlorophyll gradient, sea surface height anomaly, eddy kinetic energy, surface wind speed, and surface current speed. Atlantic Bluefin Tuna exhibited breeding behavior in the western GOM and the frontal zone of the Loop Current. Breeding areas used by the Bluefin Tuna were significantly associated with bathymetry, SST, eddy kinetic energy, surface chlorophyll concentration, and surface wind speed, with SST being the most important parameter. The Bluefin Tuna exhibited significant preference for areas with continental slope waters (2,800–3,400 m), moderate SSTs (24–25 and 26–27°C), moderate eddy kinetic energy (251–355 cm2 s−2), low surface chlorophyll concentrations (0.10–0.16 mg m−3), and moderate wind speeds (6–7 and 9–9.5 m s−1). A resource selection function of the Bluefin Tuna in the GOM was estimated using a discrete choice model and was found to be highly sensitive to SST. These habitat utilization and preference patterns exhibited by breeding Bluefin Tuna can be used to develop habitat models and estimate the probable breeding areas of Bluefin Tuna in a dynamic environment.
Michael J. W. Stokesbury - One of the best experts on this subject based on the ideXlab platform.
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stock of origin catch estimation of Atlantic Bluefin Tuna thunnus thynnus based on observed spatial distributions
Canadian Journal of Fisheries and Aquatic Sciences, 2021Co-Authors: Emilius A Aalto, Robert J Schallert, Michael J. W. Stokesbury, Francesco Ferretti, Matthew V Lauretta, John F Walter, Barbara A BlockAbstract:Atlantic Bluefin Tuna (Thunnus thynnus) are a large, highly migratory fish distributed throughout the North Atlantic Ocean and adjacent seas currently managed as two discrete stocks: western and ea...
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estimating natural mortality of Atlantic Bluefin Tuna using acoustic telemetry
Scientific Reports, 2019Co-Authors: Barbara A Block, Rebecca Whitlock, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Steve Wilson, 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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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, 2015Co-Authors: Steven G Wilson, Robert J Schallert, Mike Castleton, Michael J. W. Stokesbury, Andre Boustany, Ian D Jonsen, James E Ganong, Aaron D Spares, Barbara A BlockAbstract:The objective of this study was to advance the use of pop-up satellite archival tags to track the migrations of Atlantic Bluefin Tuna (Thunnus thynnus) to their spawning grounds. Deployment of tags occurred in the Gulf of St. Lawrence, Canada, during fall months from 2007 to 2013. Pop-up satellite archival tags (n = 135) were attached to 125 Atlantic Bluefin Tuna (curved fork length (CFL) = 268 ± 20 cm (mean ± SD)) with the objective of keeping tags on until visitation to a spawning area or longer. A dataset of 18 800 days was acquired, which included 5800 days of time-series data from 19 recovered satellite tags. Many Atlantic Bluefin Tuna visited the Gulf of Mexico spawning grounds (74%), the mean size of which was 275 ± 14 cm (CFL ± SD, n = 49), with a measured CFL of 243 to 302 cm. These fish had a mean entry date into the Gulf of Mexico of 14 January ± 42 days (SD). The mean residency period for fish that had tracks with entrance and exit from the Gulf of Mexico was 123 ± 49 days (SD) (n = 22). Atlan...
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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, Shana Beemer, Michael J. W. Stokesbury, Charles J. Farwell, Eric D Prince, Andre Boustany, Heidi Dewar, Andrew C. Seitz, Kevin C Weng, 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.