The results obtained reveal a trophic partitioning of resources among the species in the reservoir. Regularly captured species were segregated into three feeding strategies: 1) specialists on detritus foraging (nase, a native species), 2) specialists on plankton foraging (roach, an exotic species) and 3) generalist feeders (barbel and mirror carp, native and exotic species respectively). The species occasionally captured include the predators on macroinvertebrates (trout and largemouth bass, native and exotic species respectively), and two species with omnivorous feeding habits ( white bream and common carp, exotic species).
The results of the present study suggest that the food resource use by the Joaquín Costa fish assemblage is highly dynamic and diverse. Every method of analysis of dietary data illustrates variation in the diet and foraging strategies over time for some species of the fish assemblage. On the other hand, other fish species showed little variation and were characterised by a single food category.
From the point of view of the trophic strategies, some species were specialists, others showed generalist feeding strategies, and others showed seasonal shifts from generalist to specialist and viceversa. This trophic dynamism is related with the spatial distribution and