A matter of taste: Spatial and ontogenetic variations on the trophic ecology of the tiger shark at the Galapagos Marine Reserve

• Published in: PloS one 2019-09, Vol.14 (9), p.e0222754-e0222754
• Main Authors: Salinas-de-León, Pelayo, Fierro-Arcos, Denisse, Suarez-Moncada, Jennifer, Proaño, Alberto, Guachisaca-Salinas, Jacob, Páez-Rosas, Diego
• Format: Article
• Language: English
• Subjects: Acoustic telemetry; Analysis; Animal behavior; Animal Migration - physiology; Animals; Aquatic ecosystems; Aquatic reptiles; Archipelagoes; Basins; Biology and Life Sciences; Carbon; Carbon Isotopes - metabolism; Chelonia mydas; Conservation; Darwin, Charles (1809-1882); Diet; Earth Sciences; Ecological function; Ecological monitoring; Ecology; Ecology - methods; Ecology and Environmental Sciences; Ecosystem; Ecosystem management; Ecosystems; Ecuador; Female; Fish conservation; Fish populations; Fisheries; Fishes; Fishing; Fishing (Recreation); Food; Food Chain; Food chains; Food webs; Foraging behavior; Galeocerdo cuvier; Genetic aspects; Genetic research; Genetic variation; Geography; Green turtle; Islands; Life cycles; Male; Marine Biology - methods; Marine ecology; Marine ecosystems; National parks; Nature reserves; Nesting; Nitrogen Isotopes - metabolism; Ocean basins; Oceans; Ontogeny; Philopatry; Physical Sciences; Populations; Predators; Predatory Behavior - physiology; Prey; Production management; Protection and preservation; Satellite tracking; Sea turtles; Sharks; Sharks - physiology; Snakes; Spatial variations; Stable isotopes; Statistical analysis; Tagging; Taste; Telemetry; Telemetry - methods; Turtles
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0222754

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