Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)

TEMPORETTI, P.F.; ALONSO, M.F.; BAFFICO, G.; DIAZ, M.; LOPEZ,W.

San Pablo, Brasil

Congreso; XXVI Congreso de la Sociedad Internacional de Limnología (SIL); 1995

International Association of Theoretical and Applied Limnology

Changes in water quality and fish community due to the increaseof salmonid farming activities located in Alicura reservoir were studied in affected and non affected sites. The calculated nutrient loads that are introduced in the reservoir by present (450 ton/yr) salmonid production are 15 TnP/yr and 60 TnN/yr, a significant portion of natural loads. The site affected by fish farming increased nutrient concentrations and periphyton biomass, while chl a was similar to control site. In the sediments below cages., TP and OM increased 12 and 4 times, respectively. After 48 hs of incubation, contaminated sediments released SRP and NNH4. Algae growth bioassays showed a higher answer in incubations with contaminated sediments with respect to the control due to the increase of P-labil and P-OM fractions. The main species present in the gillnet catches were tha authoctonous Percichthys trucha, Patagonina hatcheri and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, and Salmo salar sebago. About 50 % of the total catch consisted of salmonids. A major portion of the CPUE in weight was composed by rainbow trout and perca. In relation with previous studies, it becomes apparent a change in the composition and the well being of the fish community. This change could not only be related with the raise in the fish farming activities.