Assembleias de peixes em áreas de balneários, Rio Negro, AM

Abstract

This study herein was an analysis of the fish assemblages in four public swimming beaches, Açutuba, Lua, Ponta Negra and Novo Airão, in the rio Negro basin, Central Amazon, approaching composition, richness and abundance of species, betweeng high and low waters, and, diurnal and nocturnal periods, in 2014. The caugths were made with trawls with different mesh and sizes. A total of 6,718 specimens were sampled, belonging to eight orders, 25 families and 142 species, respectively 84, 62, 62, and 48 species at each public swimming beaches. The composition of fish assemblages grouped jointly Açutuba and Novo Airão versus Ponta Negra and Lua, both in high and low waters. This similarity might be related to the characteristics of each beach by the presence of vegetation, substrate types, and the exclusivity of some species in the two clusters. At the beaches Açutuba and Novo Airão were common the presence of submerged vegetation, emergent and marginal ones, also the variety of substrates and the presence of seven unique species: Apistogramma gephyra, Centromochlus macracanthus, Charax pauciradiatus, gracilis Hemiodus, Hyphessobrycon dorsalis, Pimelodella megalops and Trachydoras Microstomus. At the Ponta Negra and Lua beaches did not have little or no submerged vegetation, emergent and marginal, and the sand was the only predominant substrate as well as the exclusive presence of four species: Anchoviella juruasanga, Auchenipterichthys coracoideus, Hassar Orestis and Pimelodus gr. blochii. The composition, richness and abundance of species had significant differences between diurnal and nocturnal periods, while just composition and abundance of species in relation to the flood cycle, high and low waters. The beach Açutuba had higher composition, richness and abundance of species among public swimming beaches. Characiformes composed the greatest richness and abundance of species in the total samplings, followed by Siluriformes, Perciformes, Clupeiformes, Gymnotiformes, Rajiformes, Beloniformes, and Pleuronectiformes. The richest families in descending order were: Characidae, Doradidae, Auchenipteridae, Cichlidae and Engraulidae. At total, the characids Lonchogenys ilisha, Rhinobrycon negrensis, and Microschemobrycon casiquiare were the most abundant species. The assemblages studied in the rio Negro public swimming beaches had relative high species diversity in terms of composition and richness species, well as in abundance of species, though being under pressure of different anthropogenic disturbance, such as wastings disposals and the entry of people in the water.