Influência de fatores ambientais e da intensidade da pesca nas assembleias de peixes de uma sub-bacia no médio Rio Negro, Amazonas, Brasil

Abstract

The Negro river basin, in the northwest portion of the Amazon, it's a very complex system which has a high diversity of fish. Identify the factors that explain this diversity is a challenge for science and fundamental for development conservation strategies. The seasonal hydrological cycle is a very important factor, as it guarantees availability of the different habitats, providing greater amount of food. However, in the region different fishing modalities are practiced: subsistence, ornamental, commercial and sport fishing, being the main activity of the population since ancient times. However, the present study assesses the influence of environmental factors and the intensity of fishing on fish assemblages in a sub-basin in the middle Negro river. For this, six sampling points were sampled (Aracá river, Demeni river and Confluence) through experimental fisheries in two phases totaling twelve samplings. From the data ecological descriptors of fish assemblages were estimated in a total of 3.178 fish caught, the Characiformes, Siluriformes and Cichliformes being the orders that presented greatest riches. The species richness varied from 19 to 58 species and the abundance varied between 90 and 567 individuals for the two hydrological periods, the Shannon index was similar in both periods with estimates between 2.00 and 3.38, equitability and dominance (P = 0.64, P = 0.19) was also found to be similar between periods. Beta diversity standards in the Aracá-Demeni sub-basin are caused by species substitution. The fish assemblages are influenced by environmental variables, conductivity and dissolved oxygen (r2 = 51.9%). With regard to fishing, the regressions showed a correlation between richness (S) and fishing intensity (IP) Pseudo-R2=0.53, and diversity (H´) and fishing intensity (IP) Pseudo-R2=0,44, showing that middle of the Negro river the fishing activity may be influencing the structure of the fish assemblies. The results show that seasonality, spatial factors and fishing exert influence on fish assemblages in the Aracá-Demeni sub-basin, middle of the Negro river.