Composição específica e a abundância da ictiofauna em ambientes de praias no baixo rio Negro, Amazonas, Brasil

Abstract

The objective of this study was to characterize the richness, abundance, species composition and trophic aspects of fish assemblages found in the beach environment of the lower Negro River during the dry season (2016). A total of 8492 specimens of fish were collected, belonging to 11 orders, 35 families, 97 genera and 143 species distributed between the beaches of Anavilhanas, Tupé and Costa do Tatu. The composition of the assemblies revealed the dominance of the orders Characiformes, Siluriformes, Perciformes, Gymnotiformes, Clupeiformes and Myliobatiformes. These orders together accounted for 96.5% of the total, completing the rest of the orders with only one individual each being Belongiformes Cypriniformes, Pleuronectiformes, Synbranchiformes and Tetraodontiformes with the remaining 3.5%. The ten most abundant families were Characidae, Cichlidae, Doradidae, Loricaridae, Auchenipteridae, Engraulidae, Sternopygida, Serrasalmidae, Acestrorhynchidae and Anostomidae. The most abundant species were Lonchogenys ilisha, Eigenmannia macrops, Amazonsprattus scintilla, Triportheus albus, Moenkhausia megalops, Hemigrammus levis, Eigenmannia virescens, Trachydoras microstomus, Moenkhausia lepidura and Geophagus proximus, representing together 54.4% of the abundance. The nocturnal samplings on the beaches of the lower Negro River presented higher values of richness, abundance, diversity and biomass than samplings carried out during the daytime period. The physical-chemical variables presented average values within the expected for the dry season in the Negro River. The beaches of Anavilhanas and Costa do Tatu did not show any signs of anthropogenic disturbance. Only the Tupé beach had a lot of discarded material (garbage) during the dry season in its waters, which may be indicative of a possible environmental change.