Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags

Walli, Andreas; Teo, Steven L. H.; Boustany, André M.; Farwell, Charles J.; Williams, Tom; Dewar, Heidi; Prince, Eric D.; Block, Barbara A.

doi:10.1371/journal.pone.0006151

Cited by 152 publications

(167 citation statements)

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“…1D). For these analyses, we used an effort-corrected index of occurrence per unit area (number of mean days per grid cell) (22) to reduce biases from tagging location and track length (SI Appendix, Fig. S2 and SI Materials and Methods 1.3).…”

Section: Resultsmentioning

confidence: 99%

Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

Queiroz

Humphries

Mucientes

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

197

219

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Overfishing is arguably the greatest ecological threat facing the oceans, yet catches of many highly migratory fishes including oceanic sharks remain largely unregulated with poor monitoring and data reporting. Oceanic shark conservation is hampered by basic knowledge gaps about where sharks aggregate across population ranges and precisely where they overlap with fishers. Using satellite tracking data from six shark species across the North Atlantic, we show that pelagic sharks occupy predictable habitat hotspots of high space use. Movement modeling showed sharks preferred habitats characterized by strong sea surface-temperature gradients (fronts) over other available habitats. However, simultaneous Global Positioning System (GPS) tracking of the entire Spanish and Portuguese longline-vessel fishing fleets show an 80% overlap of fished areas with hotspots, potentially increasing shark susceptibility to fishing exploitation. Regions of high overlap between oceanic tagged sharks and longliners included the North Atlantic Current/Labrador Current convergence zone and the Mid-Atlantic Ridge southwest of the Azores. In these main regions, and subareas within them, shark/vessel co-occurrence was spatially and temporally persistent between years, highlighting how broadly the fishing exploitation efficiently "tracks" oceanic sharks within their space-use hotspots year-round. Given this intense focus of longliners on shark hotspots, our study argues the need for international catch limits for pelagic sharks and identifies a future role of combining fine-scale fish and vessel telemetry to inform the ocean-scale management of fisheries.animal telemetry | distribution | conservation | fisheries | predator-prey O ceanic pelagic sharks are iconic top predators with relatively low resilience to exploitation (1-3), yet many tens of millions of individuals are caught each year by high-seas fisheries (2) with significant reductions in catch rates documented for many species (4-6). This level of exploitation is especially problematic because the harvest of oceanic sharks remains largely unregulated (2, 7). For the majority of shark species that make up more than 95% of oceanic shark catches, no international or bilateral harvest limits have been imposed (2, 7). Consequently, analysis indicates that extinction risk in oceanic and coastal sharks and rays is higher than for most other vertebrates (3). Accordingly, there is a critical need and concern for improved management and conservation of oceanic sharks.Management action for oceanic sharks such as catch quotas, size limits, and/or area closures (i.e., marine protected areas, MPAs) is hampered by a paucity of high-quality data on total catches, landings, species identification, catch locations, and the susceptibility of sharks to fisheries (2, 4, 7). In addition, poor recordkeeping, a lack of reporting or deliberate underreporting of pelagic shark catches by the high seas longlining fleet and/or fishing nations (7), contributes to poor data quality that can lead to increased unce...

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Section: Resultsmentioning

confidence: 99%

Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

Queiroz

Humphries

Mucientes

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

197

219

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“…In bluefin tuna, thermal gradients of approximately 108C are common between ambient sea surface and internal body temperatures, and can increase to approximately 208C when diving into cool waters [1,2,39]. Thus, the bluefin tuna heart must supply the high oxygen demand of warm tissues while functioning across a wide range of temperatures.…”

Section: Discussionmentioning

confidence: 99%

Warm fish with cold hearts: thermal plasticity of excitation–contraction coupling in bluefin tuna

et al. 2010

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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 Ca ] 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 D[Ca 2þ ] i by increasing intracellular Ca 2þ 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 Ca 2þ cycling is the malleable unit of cellular Ca 2þ 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.

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“…Electronic tags (e.g. acoustic, archival, and satellite) equipped with pressure sensors are an appropriate tool for observing vertical movements of pelagic fish in their habitat (Bach et al 2003, Musyl et al 2003, Schaefer et al 2009, Walli et al 2009, Stevens et al 2010. Longlines equipped with time-depth recorders (TDRs) and hook timers provide information on the time and depth of capture for many pelagic species (Boggs 1992, Bach et al 2003, Bigelow et al 2006.…”

Section: Introductionmentioning

confidence: 99%

Comparative analysis of depth distribution for seventeen large pelagic fish species captured in a longline fishery in the central-eastern Pacific Ocean

Zhu¹,

Xu²,

Dai³

et al. 2011

Sci. Mar.

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SUMMARY: The objective of this study was to estimate depth distribution of pelagic species captured in a longline fishery and to evaluate the difference in depth distribution among species. We estimated depth distribution for 17 frequently captured species based on a Chinese longline fishing trip targeting bigeye tuna (Thunnus obesus) in the central-eastern Pacific Ocean in February-November 2006. The depth distributions of 13 bycatch species were significantly different from that of bigeye tuna. Although most of the bycatch species were found to be distributed in water depths shallower than bigeye tuna (i.e. increasing hook depths can decrease catch rates of these species), the rates of catch rates declined with increasing hook depths may be different. The depth distributions were found to be not significantly different between genders for 7 species. There was no significant correlation between fish sizes and capture depths. The information derived from this study can play an important role in reducing bycatch in pelagic tuna longline fisheries in the central-eastern Pacific Ocean.Keywords: pelagic fish, tuna, bycatch, vertical distribution, longline, Pacific Ocean. RESUMEN: Análisis comparativo de la distribución en profundidad de diecisiete especies de grandes pelági-cos, capturados en una pesquería de palangre en el océano Pacífico centro-oriental. -El objetivo de este estudio ha sido estimar la distribución en profundidad de especies pelágicas capturadas en una pesquería de palangre y evaluar la diferencia en la distribución en profundidad entre las especies. Se estimó la distribución en profundidad para 17 especies capturadas frecuentemente, sobre la base de los datos obtenidos en una marea de una pesquería de palangre china dirigida al patudo (Thunnus obesus) en el océano Pacífico centro-oriental, durante febrero-noviembre 2006. Las distribuciones en profundidad de 13 especies no objetivo de la pesquería fueron significativamente diferentes de la del patudo. Aunque la mayoría de estas 13 especies se encontraron a menor profundidad que el patudo, la medida en la que la captura acompañante disminuye puede ser diferente al situar los anzuelos a mayor profundidad. En 7 de las especies no se encontraron diferencias significativas entre sexos en relación a la distribución en profundidad. No hubo correlación significativa entre los tamaños de los peces y las profundidades de captura. La información derivada de este estudio puede jugar un rol importante en la reducción de la captura acompañante de pesquerías pelágicas con palangre dirigidas a captura de atunes en el océano Pací-fico centro-oriental.

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Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags

Cited by 152 publications

References 64 publications

Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

Ocean-wide tracking of pelagic sharks reveals extent of overlap with longline fishing hotspots

Warm fish with cold hearts: thermal plasticity of excitation–contraction coupling in bluefin tuna

Comparative analysis of depth distribution for seventeen large pelagic fish species captured in a longline fishery in the central-eastern Pacific Ocean

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