The trophic ecology of Caribbean reef sharks (Carcharhinus perezi) relative to other large teleost predators on an isolated coral atoll
Bulk stable isotope analysis was used to assess the trophic level and foraging habitats of Caribbean reef sharks (Carcharhinus perezi) compared to three large sympatric predatory teleosts (the Nassau grouper Epinephelus striatus, black grouper Mycteroperca bonaci, and great barracuda Sphyraena barracuda) in an isolated Caribbean coral reef ecosystem. Models and empirical studies have suggested that the depletion of large-bodied sharks in coral reef ecosystems triggers a trophic cascade that could affect the benthic community, favoring algae over coral. The hypothesized cascade is based on the premise that sharks prey on large piscivorous teleost fish that in turn prey on key herbivorous fish. Analysis of nitrogen-stable isotopes (δ15N) from white muscle tissue revealed neither adult or juvenile Caribbean reef sharks were significantly enriched in 15N compared with sympatric predatory teleost species. Linear regression found no evidence of an ontogenetic increase in nitrogen with increasing body size for Caribbean reef sharks; however, there was a significant positive relationship between body size and carbon isotope (δ13C) values. These results suggest that Caribbean reef sharks in isolated systems do not act as the apex predator in coral reef ecosystems primarily feeding on large-bodied sympatric teleosts. Instead, Caribbean reef sharks form part of an upper trophic-level predator guild alongside large-bodied teleosts, which makes the predicted trophic cascade as a result of the removal of reef sharks unlikely. Moreover, the body size–δ13C relationship suggests Caribbean reef sharks exhibit ontogenetic and individual variation in where they feed. The ecological role of this species is, therefore, complex and contextual, similar to carcharhinid species in the Indo-Pacific, emphasizing the need to further elucidate the interactions between reef sharks and the overall coral reef ecosystem so as to best inform effective conservation and management of the species.
This research was funded by grants from Earthwatch International (to DDC and EAB) and the Roe Foundation (to DDC). We would like to thank all the Earthwatch volunteers and Dr. Alex Tilley for their tireless efforts collecting the samples, and for providing additional samples, respectively. Captain Norlan Lamb, Ashbert Miranda, and the management and staff of Wildlife Conservation Society Belize and the Glover’s Reef Research Station provided outstanding logistical support. Furthermore, thanks to Anna Hussey and Aaron Fisk for assistance and mentorship in the lab and the Stony Brook students who helped prepare the samples.
This work was funded by grants from Earthwatch International (Grant number 7262541).
Compliance with ethical standards
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of Stony Brook University and this work was carried out under the necessary research and animal care permits from the Government of Belize Ministry of Agriculture and Fisheries.
Conflict of interest
The authors declare that they have no conflicts of interest.
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