Relaciones tróficas de Trucha Marrón, Salmo fario Linné, y Trucha Arco Iris, Salmo gairdneri Richardson, (Osteichthyes, Salmoniformes) en un embalse norpatagónico

Abstract

A detailed comparative study of the diet of wild brown and rainbow trout in the Ramos Mexía reservoir, Neuquén Province, during 1982 and 1983 was made. The seasonal composition of both diets was determined, calculating number, volume, and occurrence. The feeding habits of the brown trout are based mainly on perch, silverside, galaxiids, molluscs, and crustaceans; for rainbow trout, galaxiids, terrestrial insects, ostracods, crustaceans, and molluscs were recorded. Fishes were mainly caught throughout the year by brown trouts, while rainbow trouts capture mostly ostracods during spring and galaxiids throughout the rest of the year. A decrease in the percentage of galaxiids, insects, and molluscs was observed with the increase of brown trout size, while increasing that of silverside. Rainbow trouts also showed an increase in perch and galaxiids predation with size, with a decrease in crustaceans and insects. A diet overlap was recorded only in spring. Trouts occupy both the 3rd and 5th level in the trophic chain, being very active ichthyofagous predators.