Pelagic Fish Communities and Eutrophication in Lakes of an Andean Basin of Central Chile

Abstract

ABSTRACT Biomass, production, and yield of the pelagic fish communities were estimated in Laguna Grande of San Pedro (eutrophic), Laguna Chica of San Pedro (mesotrophic) and Lake Icalma (oligotrophic), all belonging to the Andean basin of the Biobío river (36°45′-39°S), Chile. Fish biomass showed differences that were related to the trophic state of the lakes. The highest biomasses were in the eutrophic lakes, with mean values of 563 kg ha−1 in Laguna Grande of San Pedro and 591 kg ha−1 in Laguna Chica of San Pedro. The lowest biomass was in Lake Icalma with a mean of 164 kg ha−1. The estimated annual yields were 170 kg ha−1 in Laguna Grande of San Pedro, 157 kg ha−1 in Laguna Chica of San Pedro, and 32 kg ha−1 in Lake Icalma. In Laguna Grande of San Pedro, the highest percentage of fish yield was the non-salmonid species, including Cyprinids (Cyprinus carpio and Carassius carassius) with 87.2%, and only 12.8% was Oncorhynchus mykiss, the only salmonid species in this lake. The same pattern was observed in Laguna Chica of San Pedro, with 78.6% for Odontesthes bonariensis and 21.4% for O. mykiss. In Lake Icalma the pattern was opposite, with a 90.2% for the salmonid species (O. mykiss and Salmo trutta) and only 9.8% for Percichthys trucha.