Vertical movement patterns and ontogenetic niche expansion in the tiger shark, Galeocerdo cuvier.
TLDR
A clear ontogenetic expansion in the vertical range of tiger shark habitat was observed, with generalized linear models estimating a ~4-fold increase in maximum diving depth from 150- to 300-cm size-classes.Abstract:
Sharks are top predators in many marine ecosystems and can impact community dynamics, yet many shark populations are undergoing severe declines primarily due to overfishing. Obtaining species-specific knowledge on shark spatial ecology is important to implement adequate management strategies for the effective conservation of these taxa. This is particularly relevant concerning highly-mobile species that use wide home ranges comprising coastal and oceanic habitats, such as tiger sharks, Galeocerdo cuvier. We deployed satellite tags in 20 juvenile tiger sharks off northeastern Brazil to assess the effect of intrinsic and extrinsic factors on depth and temperature usage. Sharks were tracked for a total of 1184 d and used waters up to 1112 m in depth. The minimum temperature recorded equaled 4°C. All sharks had a clear preference for surface (< 5 m) waters but variability in depth usage was observed as some sharks used mostly shallow (< 60 m) waters whereas others made frequent incursions into greater depths. A diel behavioral shift was detected, with sharks spending considerably more time in surface (< 10 m) waters during the night. Moreover, a clear ontogenetic expansion in the vertical range of tiger shark habitat was observed, with generalized linear models estimating a ~4-fold increase in maximum diving depth from 150- to 300-cm size-classes. The time spent in the upper 5 m of the water column did not vary ontogenetically but shark size was the most important factor explaining the utilization of deeper water layers. Young-of-the-year tiger sharks seem to associate with shallow, neritic habitats but they progressively move into deeper oceanic habitats as they grow larger. Such an early plasticity in habitat use could endow tiger sharks with access to previously unavailable prey, thus contributing to a wider ecological niche.read more
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Patterns and drivers of vertical movements of the large fishes of the epipelagic
Samantha Andrzejaczek,Samantha Andrzejaczek,Adrian C. Gleiss,Charitha Pattiaratchi,Mark G. Meekan +4 more
TL;DR: It is proposed that patterns of vertical movement in gill-breathing animals of the epipelagic are best characterised by the need to move continuously in a three-dimensional environment while optimising food encounter and energy expenditure, avoiding predators, searching for mates and remaining within the limits imposed by the physical environment on their physiology.
Journal ArticleDOI
Ontogeny of Head and Caudal Fin Shape of an Apex Marine Predator: The Tiger Shark (Galeocerdo Cuvier)
TL;DR: Changes in the shape of the head and caudal fin of tiger sharks across ontogeny are interpreted as a result of two ecological transitions, which could have effects for other species that tiger sharks consume and interact with.
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Behavioral evidence suggests facultative scavenging by a marine apex predator during a food pulse
Neil Hammerschlag,Ian Bell,Richard Fitzpatrick,Austin J. Gallagher,Lucy A. Hawkes,Mark G. Meekan,John D. Stevens,Michele Thums,Matthew J. Witt,Adam Barnett +9 more
TL;DR: Movement analyses of tiger shark and green turtle movement and surfacing behavior at Raine Island suggest that facultative scavenging may be a prevalent, yet underappreciated, feeding strategy in tiger sharks.
Journal ArticleDOI
Inferring trends and linkages between shark abundance and shark bites on humans for shark-hazard mitigation
TL;DR: Generalised additive models showed that the frequency of shark bites was directly proportional to and followed the same seasonal trends as PDS abundance, meeting the hypothesis that higher shark abundance may result in an increased chance of a shark bite.
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Mercury isotopes as tracers of ecology and metabolism in two sympatric shark species
Gaël Le Croizier,Anne Lorrain,Jeroen E. Sonke,Sébastien Jaquemet,Gauthier Schaal,Marina Renedo,Lucien Besnard,Yves Cherel,David Point +8 more
TL;DR: Unexpectedly, a positive shift in δ202Hg (>1‰) between sharks and their prey is found, indicating that sharks may display strong MeHg demethylation abilities, possibly reflecting evolutionary pathways for mitigating their MeHG contamination.
References
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Book
Sharks of the World: an Annotated and Illustrated Catalogue of Shark Species Known to Date
TL;DR: Sharks of the world :an annotated and illustrated catalogue of shark species known to date as mentioned in this paper, is an annotated catalogue of sharks species known in the wild and has been published for the first time.
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The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems
TL;DR: The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems are examined at the single-species level and through trophic interactions.
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Collapse and Conservation of Shark Populations in the Northwest Atlantic
Julia K. Baum,Ransom A. Myers,Daniel G. Kehler,Boris Worm,Shelton J. Harley,Penny A. Doherty +5 more
TL;DR: Open-area models highlight priority areas for shark conservation, and the need to consider effort reallocation and site selection if marine reserves are to benefit multiple threatened species.
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Predicting ecological consequences of marine top predator declines
TL;DR: The consequences of marine predator declines are outlined and an integrated predictive framework that includes risk effects is proposed, which appear to be strongest for long-lived prey species and when resources are abundant.