Feeding strategy of the exotic Rainbow trout (Oncorhynchus mykiss) at low order Patagonian streams

DI PRINZIO CECILIA; MISERENDINO MARIA LAURA; CASAUX RICARDO

FISHERIES MANAGEMENT AND ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Singapur; Año: 2013 vol. 20 p. 414 - 425

0969-997X

During 2005-2006 we studied the diet composition and the feeding strategy of the Rainbowtrout (Oncorhynchus mykiss) at two low order Patagonian streams. Benthic Macroinvertebrate  availability was estimated at both riffles and pools. Fish stomach contents were examined to  determine prey richness and diversity, prey selectivity, food-niche width, and the feeding  strategy employed by trouts along the year. Benthos availability varied seasonally, Ephemeroptera, Trichoptera, Plecoptera and Diptera species dominated in samples. Rainbow trout diet was composed mainly by benthic macroinvertebrates, followed by terrestrial insects, fish, algae and plants. Different trout size-classes segregated the use of food resources to reduce the predation pressure. Selected preys included organisms displaying none to high mobility. A high feeding plasticity allows trout to buffer changes in food availability by switching from a specialized to a generalized feeding behavior. Consequently, trout may opportunistically exploit abundant but temporary food resources, which would explain their marked expansion in Patagonia environments.