Dieta y estrategia de alimentación de la merluza común Merluccius Hubbsi del Golfo San Matías, Río Negro

Abstract

La merluza común, Merluccius Hubbsi, es la especie blanco histórico de la pesquería demersal del Golfo San Matías y constituye una de las especies claves en las cadenas tróficas del ecosistema marino patagónico y del Golfo en particular. La merluza se comporta como un predador oportunista, mostrando preferencia por los crustáceos planctónicos durante la etapa juvenil y por otros numerosos taxones (incluyendo un alto grado de canibalismo) en la etapa adulta. Los cambios observados durante los últimos años en la abundancia de algunas especies del Golfo, en particular los incrementos en los stocks de langostino Pleoticus Muelleri y langostilla Munida Gregaria, podrían estar produciendos importantes cambios en la estructura de las tramas tróficas. La hipótesis de trabajo de este estudio es que los cambios de abundancia de algunas especies en el ecosistema se ven reflejados en la dieta de la merluza común, ya que los peces son capaces de cambiar su dieta y comportamiento alimentario en respuesta a la disponibilidad de presas. La alimentación es un factor importante en la regulación de las poblaciones de peces, por lo tanto toda información sobre este tema constituye al conocimiento necesario para un mejor manejo de la pesquería.

The Argentine hake, Merluccius hubbsi, has been the main target species of the San Matías Gulf (SMG) demersal fishery while it is a key species of the trophic web of the Patagonia Marine Ecosystem and the Gulf in particular. Merluccius hubbsi is an opportunistic predator, showing preference for crustacean when small, whereas medium-siaed and large hakes prey over numerous taxa at lower frequency (including high level of cannibalism). Changes observed in recent years in the abundances of some species in SMG, particularly the increase in Argentine Red shrimp Pleoticus muelleri and squat lobster Munida gregaria stocks, could be producing important changes in the structure of the food web. Since hakes are able to change their diet and eating behavior in response to the availability of prey, the hypothesis proposed here is that changes in the abundances of some species are reflected in the diet of the Argentine hake. The feeding is an important factor in the regulation of fish stocks, therefore all the information on this subject contributes to the knowledge necessary for a better management of the fisheries. The last study available about the diet of the Argentine hake from the Gulf was made based on data collected a decade ago when the abundances of Pleoticus muelleri and Munida gregaria were relatively low; this is why the present study constitutes a critical update of this information, considering the constant evolution of the fishery. Based on this hypothesis, the aim of this study was to characterize the diet of the Argentine hake taking into account the species composition (frequency of occurrence, weight, number and relative abundance) and its feeding strategy. The species found in the stomachs belonged to four taxonomical groups, including 14 species (3 fish, 4 molluscs, 6 crustaceans and 1 bryozoo). Argentine hake fed mainly on Munida gregaria (%IRI 72,19%), followed by Peisos petrunkevitchi (oIRI 19,04%) and M. hubbsi (%IRI 7,95%). Most preys were Escaneado con CamScanner Tesis de Licenciatura Rosana Alonso consumed occasionally and in low abundance, which is common for generalist and opportunistic predators. Based on these results, I conclude that Argentine hake constitutes a key predator on the trophic web of the demersal-pelagie community of the San Matías Gulf, showing feeding habits that vary according to the abundance of their prey.