Trophic ecology of the Argentine goatfish, Mullus argentinae (Mullidae) from off northern Argentina: ontogenetic and regional diet shifts

Abstract

The Argentine goatfish Mullus argentinae is a small, endemic and demersal-benthic species that occurs in the Southwestern Atlantic Ocean (SWA). Knowledge of the trophic ecology of this species is key to understanding its role as predator in this marine region. The aim of this study was to determine the feeding habits of M. argentinae in the coastal waters off northern Argentina (36°–41°S). Stomachs from 263 individuals ranging from 82 to 267 mm total length (TL) were analyzed. The effects of TL, maturity stage and region on the diet composition of this species were evaluated, using a multiple hypothesis modeling approach. Mullus argentinae fed primarily on amphipods, followed by polychaetes, shrimps and bivalves. Cumaceans, brachyuran crabs, echinoderms and isopods were consumed in less proportion. The dietary composition of M. argentinae showed shifts with increasing body size, maturity stage and also between regions. As this species increased in size, the consumption of polychaetes, shrimps and bivalves was higher, but the consumption of amphipods decreased. In addition, mature individuals preyed more heavily on echinoderms, and immature individuals consumed more cumaceans. Moreover, this species is able to consume larger shrimps and brachyuran crabs as it grows, but it does not abandon the consumption of small decapod crustaceans. Mullus argentinae presents regional variations in its diet between three oceanographic distinct regions along the coast. The regional variability is characterized by a south-north gradient in the type of prey consumed. This investigation helps to increase the knowledge of the trophic role of M. argentinae, providing a baseline for future investigations in the SWA.