Trophic relationships of 13 small to medium-sized elasmobranchs in Central Patagonia, Southwestern Atlantic

Abstract

We assessed the trophic roles of 13 medium-sized elasmobranchs in Central Patagonia (41°–47° S) by identifying their interspecific relationships and trophic overlap using stomach contents and δ¹⁵N and δ¹³C values. Specimens were collected from the bycatch of the Patagonian red shrimp Pleoticus muelleri trawling fishery and from the sport coastal fishing in areas without trawling. Results showed spatial differences in the diet composition of species between capture sites and from those previous diets reported for Argentina. Trophic positions assessment showed a group of top predators (TP ~ 4) and mesopredators (TP ~ 3.5). Three trophic guilds were identified for the chondrichthyan species recorded in the coastal and deep zones. We also found a dietary overlap among almost all elasmobranch species mainly related to the consumption of the shrimp P. muelleri. Despite not being reported previously in the diet of studied species, we consider the high consumption of this shrimp as an expected result for demersal mesopredators captured in shrimp fishing grounds. These findings underscore the importance of continually updating trophic information in a global change scenario to contribute scientific evidence to the development of adaptative management.