The opportunistic sense: The diet of Argentine hake Merluccius hubbsi reflects changes in prey availability

Abstract

Changes in the abundance of some species in the San Matías Gulf (north Patagonia, Argentina) have been observed in recent years; in particular increases in crustaceans populations that could be influencing the trophic relationships and food web structure. The Argentine hake Merluccius hubbsi has been the main demersal resource that supports a fishery since 1971. Given that M. hubbsi is a generalist and opportunistic predator, its diet from the perspective of specific composition and feeding strategy was evaluated. Fourteen species were identified belonging to four zoological groups (3 fishes, 4 molluscs, 6 crustaceans and 1 bryozoan). The most commonly consumed prey was the lobster krill Munida gregaria (index of relative importance -%IRI- 72.19%) followed by the white shrimp Peisos petrunkevitchi (%IRI 19.04%) and M. hubbsi (%IRI 7.95%). Most prey were infrequently consumed and at low abundances, which it is common for a generalist-opportunistic predator. Substantial changes in the diet composition were detected when compared to a previous study, showing a large increase in crustacean occurrence in concordance with the abundance changes observed in the environment. The results from this study highlighted the importance to consider information about population trends and trophic relationships to better understand the dynamics of marine communities under exploitation.