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  • 1
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 75, No. 4 ( 2018-07-01), p. 1383-1392
    Abstract: The ability to predict animal movement based on environmental change is essential for understanding the dynamic nature of their spatial ecology, and in turn the effectiveness of conservation strategies. We used a large marine predator that displays partial migration (the tiger shark Galeocerdo cuvier) as a model to test the role of oceanic conditions in predicting the space-use of different size classes. By using generalized additive mixed models (GAMMs), we revealed that environmental variables (sea surface temperature, primary productivity, thermal fronts, and bathymetry) had much greater predictive power for the movements of large, migratory tiger sharks than for small, resident individuals. We also found that coverage of tiger shark movements within “shark sanctuaries” (protected areas specifically for sharks) in the northwest Atlantic could be increased from 12 to 52% through inclusion of Bermuda’s waters. However, as large tiger sharks are migratory, over 80% of potential longline fisheries interactions would still occur outside the boundaries of even the expanded protected areas. This emphasises that management of highly migratory species needs to be dynamic and account for changing interactions with fisheries over time, which in a changing climate may rely on predicting movements based on oceanic conditions to be effective.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2018
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    detail.hit.zdb_id: 29056-7
    SSG: 12
    SSG: 21,3
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  • 2
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 5, No. 1 ( 2015-06-09)
    Abstract: Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier , we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2015
    detail.hit.zdb_id: 2615211-3
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  • 3
    In: Ecology and Evolution, Wiley, Vol. 4, No. 10 ( 2014-05), p. 1768-1786
    Abstract: Tiger sharks ( Galeocerdo cuvier ) are a wide ranging, potentially keystone predator species that display a variety of horizontal movement patterns, making use of coastal and pelagic waters. Far less, however, is known about their vertical movements and use of the water column. We used pop‐up satellite archival tags with two data sampling rates (high rate and standard rate tags) to investigate the vertical habitat use and diving behavior of tiger sharks tagged on the Puerto Rico–Virgin Islands platform and off Bermuda between 2008 and 2009. Useable data were received from nine of 14 sharks tagged, tracked over a total of 529 days. Sharks spent the majority of their time making yo‐yo dives within the upper 50 m of the water column and considerable time within the upper 5 m of the water column. As a result, sharks typically occupied a narrow daily temperature range (~2°C). Dives to greater than 200 m were common, and all sharks made dives to at least 250 m, with one shark reaching a depth of 828 m. Despite some similarities among individuals, a great deal of intraspecific variability in vertical habit use was observed. Four distinct depth distributions that were not related to tagging location, horizontal movements, sex, or size were detected. In addition, similar depth distributions did not necessitate similar dive patterns among sharks. Recognition of intraspecific variability in habitat use of top predators can be crucial for effective management of these species and for understanding their influence on ecosystem dynamics.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2014
    detail.hit.zdb_id: 2635675-2
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