A matter of taste: Spatial and ontogenetic variations on the trophic ecology of the tiger shark at the Galapagos Marine Reserve.
Pelayo Salinas-de-León,Denisse Fierro-Arcos,Jennifer Suarez-Moncada,Alberto Proaño,Jacob Guachisaca-Salinas,Diego Páez-Rosas +5 more
TLDR
Stable isotope analysis, satellite tracking, and passive acoustic telemetry data suggest that tiger sharks in the Galapagos could be segregated into specific populations separated by geographical scales of <100 km, and additional studies using genetic tools could provide further evidence on the presence of separate management units.Abstract:
Sharks are top predators across ocean food webs and have a major ecological role in marine ecosystems. Investigating the trophic ecology of this group of species is thus essential to understand ecosystem functioning and inform specific management actions aimed at shark conservation. The Galapagos Islands represent one of the last ocean wildernesses, where populations of sharks and other top marine predators come close to a pristine status. Here we provide the first study on the trophic ecology of the tiger shark (Galeocerdo cuvier) within the Galapagos Marine Reserve (GMR), using a combination of stable isotope analysis, satellite tracking, and passive acoustic telemetry to investigate ontogenetic and spatial variations at two regions. The mean estimated δ13C and δ15N at Isabela island (western region) were -13.9 ± 0.5‰ and 13.7 ± 0.7‰; and for Santa Cruz island (central region) were -13.8 ± 0.3‰ and 13.4 ± 0.7‰, respectively. Green sea turtles (Chelonia mydas) were the main prey item for large tiger sharks (>280 cm TL), while smaller sharks mainly fed on squid and pelagic fish. Tiger sharks exhibited a high degree of philopatry around green sea-turtle nesting areas, with the majority of sharks detected around green sea-turtle nesting areas for at least 10 months after their capture date, and some individuals were even present during the entire three-year study period. Although we did not report statistically significant differences between the two regions, isotopic and electronic tagging data suggest that tiger sharks in the Galapagos could be segregated into specific populations separated by geographical scales of <100 km. The high productivity of the archipelago, along with the protection from industrial fishing granted by the GMR, result in abundant and predictable sources of prey. This high food abundance, combined with the presence of suitable habitats throughout the tiger shark life cycle, might result in a reduction of migratory behaviours when compared to movement patterns of tiger sharks in other ocean basins. Additional studies using genetic tools could provide further evidence on the presence of separate management units, as it has been recently revealed for other shark species inhabiting the GMR.read more
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Dietary and reproductive biomarkers in a generalist apex predator reveal differences in nutritional ecology across life stages
TL;DR: A conceptual model of expected changes in nutritional and trophic markers across life stages of female tiger sharks is proposed.
Journal ArticleDOI
Metabolic and nutritional condition of juvenile tiger sharks exposed to regional differences in coastal urbanization
Bianca de Sousa Rangel,Renata Guimarães Moreira,Yuri Niella,James A. Sulikowski,Neil Hammerschlag +4 more
TL;DR: Findings do not suggest that the differences in nutritional quality and metabolic condition found between the two sampling locations can be fully attributed to foraging in areas exposed to differing levels of urbanization, but speculate that these patterns may be due to the highly migratory nature and generalist feeding strategy of this species, even at the juvenile life stage.
Journal ArticleDOI
Trophic variation during the early stages of blacktip sharks (Carcharhinus limbatus) within coastal nurseries of the Galapagos Marine Reserve
Diego Páez-Rosas,Jenifer Suarez-Moncada,Fernando R. Elorriaga-Verplancken,Alberto Proaño,Camila Arnés-Urgellés,Pelayo Salinas-de-León,Felipe Galván-Magaña +6 more
TL;DR: Stable isotope analysis on 57 samples from three coastal nurseries around the Galapagos archipelago evaluated the intraspecific variation in trophic shifts of four size classes of blacktip sharks.
Journal ArticleDOI
Hormone-mediated foraging strategies in an uncertain environment: Insights into the at-sea behavior of a marine predator.
Eugene J. DeRango,Jonas F. L. Schwarz,Paolo Piedrahita,Diego Páez-Rosas,Daniel E. Crocker,Oliver Krüger +5 more
TL;DR: In insights into how mechanistic constraints and environmental pressures may facilitate individual specialization in adaptive behavior in wild populations are provided, the collective effects of hormonal and ecological variation on marine foraging are highlighted.
Journal ArticleDOI
Using stable isotopes analysis to understand ontogenetic trophic variations of the scalloped hammerhead shark at the Galapagos Marine Reserve
Florencia Cerutti-Pereyra,Pelayo Salinas-de-León,Camila Arnés-Urgellés,Jennifer Suarez-Moncada,Eduardo Espinoza,Leandro Vaca,Diego Páez-Rosas +6 more
TL;DR: In this article , the authors assessed the foraging strategies and ontogenetic changes of scalloped hammerhead sharks, Sphyrna lewini, at Galapagos Marine Reserve (GMR), by analysing δ13C and δ15N signatures in different maturity stages.
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