Responses of trophic fish guilds upstream and downstream of the Balbina dam, Central Amazon, Northern Brazil

Abstract

This study compared the diversity, richness, abundance, and biomass of fish collected in three environments in the Central Amazon: (1) the reservoir of the Balbina hydroelectric dam; (2) the Uatumã River downstream of the dam; and (3) the Abacate River. Through the analysis of food resources, we determined the fish trophic guilds for each environment. We hypothesized that the undisturbed environment of the Abacate River would present the highest values of diversity, richness, abundance, and biomass, followed by the Uatumã River and the reservoir, and that there would be significant differences among the trophic guilds among the three environments. The highest taxonomic richness was observed for the Uatumã River, followed by the Abacate River and the reservoir. There was no statistical difference in the species richness of the trophic guilds among the three sampled sites, but the three areas differed in abundance. The highest value of guild biomass was observed for the Uatumã River, followed by the reservoir and the Abacate River. Characteristics of the Uatumã and Abacate River systems, such as size, greater complexity and heterogeneity of habitats, and flood regime, may be the cause of the greater species richness in these rivers, compared to the reservoir.