How many trophic roles can elasmobranchs play in a marine tropical network?

The aims of the present study were to identify the trophic roles of shark and batoid species in a tropical marine food web and to examine how ontogenetic dietary changes affect these roles. Elasmobranch species at different stages of maturity (juveniles and adults) are distributed at medium and high trophic levels (3.2-4.2), preying on numerous fish and invertebrates. Nine trophic groups comprising species at different stages of maturity were identified. Considering the maturity stages, elasmobranchs were found in five trophic groups and 37.5% of the regular equivalence nodes in the web. These species had roles as both predator and prey in four trophic levels of the web, participating in most of the roles identified, and are highly redundant in their functions as prey and mesopredators, but not in their role as top predators. The results of the present study suggest that elasmobranchs can be fundamental to the structure and function of marine food webs and highlight the need to include the effect of ontogenetic changes in the diet of these predators in future assessments of their ecological relevance.