Movements of the white shark Carcharodon carcharias in the North Atlantic Ocean

Skomal, Gregory B.; Braun, Camrin D.; Chisholm, John; Thorrold, Simon R.

doi:10.3354/meps12306

Cited by 81 publications

(107 citation statements)

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“…It is increasingly clear that pelagic fishes throughout the global ocean conduct long-range migratory movements (e.g., Block et al, 2011;Skomal et al, 2017) and connect the surface and deep ocean through meso-and bathy-pelagic dive behavior Thorrold et al, 2014). The basking sharks tagged in the present study were no exception, making some of the longest horizontal movements of any ocean species tagged to date (Block et al, 2005;Bonfil, 2005;Hays et al, 2006;Skomal et al, 2017).…”

Section: Discussionmentioning

confidence: 62%

“…The basking sharks tagged in the present study were no exception, making some of the longest horizontal movements of any ocean species tagged to date (Block et al, 2005;Bonfil, 2005;Hays et al, 2006;Skomal et al, 2017). Tagged individuals moved through several distinct water masses of the western Atlantic, and spent significant time in the mesopelagic, demonstrating the ability of basking sharks to traverse a wide range of environments from the surface to deep ocean across a 25 • C temperature range.…”

Section: Discussionmentioning

confidence: 68%

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Integrating Archival Tag Data and a High-Resolution Oceanographic Model to Estimate Basking Shark (Cetorhinus maximus) Movements in the Western Atlantic

2018

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Basking shark (Cetorhinus maximus) populations are considered "vulnerable" globally and "endangered" in the northeast Atlantic by the International Union for the Conservation of Nature (IUCN). Much of our knowledge of this species comes from surface observations in coastal waters, yet recent evidence suggests the majority of their lives may be spent in the deep ocean. Depth preferences of basking sharks have significantly limited movement studies that used pop-up satellite archival transmitting (PSAT) tags as conventional light-based geolocation is impossible for tagged animals that spend significant time below the photic zone. We tagged 57 basking sharks with PSAT tags in the NW Atlantic from 2004 to 2011. Many individuals spent several months at meso-and bathy-pelagic depths where accurate light-level geolocation was impossible during fall, winter and spring. We applied a newly-developed geolocation approach for the PSAT data by comparing three-dimensional depth-temperature profile data recorded by the tags to modeled in situ oceanographic data from the high-resolution HYbrid Coordinate Ocean Model (HYCOM). Observation-based likelihoods were leveraged within a state-space hidden Markov model (HMM). The combined tracks revealed that basking sharks moved from waters around Cape Cod, MA to as far as the SE coast of Brazil (20 • S), a total distance of over 17,000 km. Moreover, 59% of tagged individuals with sufficient deployment durations (>250 days) demonstrated seasonal fidelity to Cape Cod and the Gulf of Maine, with one individual returning to within 60 km of its tagging location 1 year later. Tagged sharks spent most of their time at epipelagic depths during summer months around Cape Cod and in the Gulf of Maine. During winter months, sharks spent extended periods at depths of at least 600 m while moving south to the Sargasso Sea, the Caribbean Sea, or the western tropical Atlantic. Our work demonstrates the utility of applying advances in oceanographic modeling to understanding habitat use of highly Braun et al. Oceanographic Modeling of Shark Movements migratory, often meso-and bathy-pelagic, ocean megafauna. The large-scale movement patterns of tagged sharks highlight the need for international cooperation when designing and implementing conservation strategies to ensure that the species recovers from the historical effects of over-fishing throughout the North Atlantic Ocean.

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Section: Discussionmentioning

confidence: 62%

Section: Discussionmentioning

confidence: 68%

Integrating Archival Tag Data and a High-Resolution Oceanographic Model to Estimate Basking Shark (Cetorhinus maximus) Movements in the Western Atlantic

2018

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“…Predicting abundance or evaluating status is more problematic for data‐poor species in which incidental captures in fisheries are rare and sporadic (Punt, Smith, & Smith, 2011). White shark are a good example: For any given population, individuals are encountered infrequently over a vast geographical range (Bonfil et al, 2005; Skomal, Braun, Chisholm, & Thorrold, 2017), interact with diverse fisheries in national and international waters (Dewar et al, 2013; Queiroz et al, 2019), and thus have limited potential for using catches to monitor absolute (as opposed to relative) abundance (Baum et al, 2003; Burgess et al, 2005; Curtis et al, 2014). A reliable time‐series of total removals for white shark in the Northwest Atlantic is not available due to the need to identify and scale up observed interactions from multiple fleets where observation rates tend to be low (Curtis et al, 2018; Dulvy et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Implications of life history uncertainty when evaluating status in the Northwest Atlantic population of white shark (Carcharodon carcharias)

Bowlby

Gibson

2020

Ecology and Evolution

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To effectively protect at‐risk sharks, resource managers and conservation practitioners must have a good understanding of how fisheries removals contribute to changes in abundance and how regulatory restrictions may impact a population trajectory. This means they need to know the number of animals being removed from a population and whether a given number of removals will lead to population increases or declines. For white shark (Carcharodon carcharias), theoretical quantities like the intrinsic rate of population increase or rebound potential (ability to increase in size following decline) are difficult to conceptualize in terms of real‐world abundance changes, which limits our ability to answer practical management questions. To address this shortfall, we designed a simulation model to evaluate how our understanding of longevity and life history variability of white shark affects our understanding of population trends in the Northwest Atlantic. Then, we quantified the magnitude of removals that could have caused historical population declines, compared these to biologically based reference points, and explored the removal scenarios which would result in population increase. Our results suggest that removals on the order of 100s of juveniles per year could have resulted in population‐level declines in excess of 60% during the 1970s and 1980s. Conservation actions implemented since the 1990s would have needed to be nearly 100% effective at preventing fishing mortality in order for the population to double in abundance over the last 30 years. Total removals from all fleets needed to be exceptionally small to keep them below biological reference points for white shark in the Northwest Atlantic. The population's inherent vulnerability to fishing pressure reaffirms the need for restrictive national and international conservation measures, even under a situation of abundance increase.

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“…Information on such broad‐scale movements has, on the whole, come from commercial fisheries research (Kenchington, ) with studies of more esoteric species emerging over recent decades via satellite telemetry and mark–recapture (Hays et al ., ; Kohler et al ., ; Sims, ). Notable examples include the pan‐Atlantic movements of spurdogfish Squalus acanthias L. 1758 (Holden, ), white Carcharodon carcharias (L. 1758) (Skomal et al ., ) and porbeagle Lamna nasus (Bonnaterre 1788) sharks (Cameron et al ., ). Genetic approaches suggest that ocean scale‐mixing may also be common for other large shark species, including both blue Prionace glauca (L. 1758) (Veríssimo et al ., ) and basking sharks Cetorhinus maximus (Gunnerus 1765) (Hoelzel et al ., ).…”

mentioning

confidence: 99%

Serendipitous re‐sighting of a basking shark Cetorhinus maximus reveals inter‐annual connectivity between American and European coastal hotspots

Johnston

Mayo

Mensink

et al. 2019

Journal of Fish Biology

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Transatlantic stock mixing in basking sharks Cetorhinus maximus is supported by low genetic diversity in populations throughout the Atlantic Ocean. However, despite significant focus on the species' movements; >1500 individual sharks marked for recapture and >150 individuals equipped with remote tracking tags, only a single record of transatlantic movment has been previously recorded. Within this context, the seredipitous re-sighting of a female basking shark fitted with a satellite transmitter at Malin Head, Ireland 993 days later at Cape Cod, USA is noteworthy.basking shark, conservation, genetic diversity, hotspot connectivity, mark-recapture, migration Transatlantic stock mixing in many large marine vertebrates is supported by low genetic diversity in populations throughout the Atlantic Ocean, but direct observations of transatlantic movement

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Movements of the white shark Carcharodon carcharias in the North Atlantic Ocean

Cited by 81 publications

References 60 publications

Integrating Archival Tag Data and a High-Resolution Oceanographic Model to Estimate Basking Shark (Cetorhinus maximus) Movements in the Western Atlantic

Integrating Archival Tag Data and a High-Resolution Oceanographic Model to Estimate Basking Shark (Cetorhinus maximus) Movements in the Western Atlantic

Implications of life history uncertainty when evaluating status in the Northwest Atlantic population of white shark (Carcharodon carcharias)

Serendipitous re‐sighting of a basking shark Cetorhinus maximus reveals inter‐annual connectivity between American and European coastal hotspots

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