Trophic ecology of four shark species in the Gulf of Salamanca, Colombian Caribbean, using multi-tissue stable isotopes analysis.

Abstract

Habitat use, feeding habits and trophic level were estimated for four shark species, Caribbean sharpnose shark Rhizoprionodon porosus, bull shark Carcharhinus leucas, juveniles of silky shark Carcharhinus falciformis and scalloped hammerhead shark Sphyrna lewini, based on stable isotope analysis (SIA) of δ¹⁵N and δ¹³C in three tissues (muscle, liver and blood) with different turnover rates. The δ¹⁵N values of R. porosus and C. leucas did not differ by sex/maturity stage or time scale. At the same time, juveniles of C. falciformis and S. lewini showed the loss of maternal isotopic signal that decreased based on the tissue scale time. The δ¹³C values indicated a shared habitat for three species: R. porosus, C. falciformis and S. lewini, the latter two with possible regional movements between coastal waters and open waters in their juvenile stage, whereas C. leucas prefers coastal waters because of a higher isotopic enrichment. The mixing model suggests that R. porosus and C. falciformis shared the most abundant prey in the ecosystem (small pelagic fish). Reef fish had a higher percentage contribution for C. leucas, whereas diet contribution of S. lewini was not clearly distinguished. All four species have trophic levels between 3.5 and 4.5, fulfilling meso- and top-predator roles, with generalist, opportunist or specialist behaviours based on isotopic niche breadth and variance comparisons.