Composition and structure of fish community of two beaches under the same type of anthropic pressure, coast of São Paulo, Brazil. Marcos Rodrigues da Costa

Abstract

The tested hypothesis was that beaches under the same type of human pressure discharge (organic) support the same structure of fish assemblages. We performed fish samples monthly in Ubatuba and Caraguá beaches using a beach seine. The patterns of seasonal and spatial similarity between the beaches were determined by cluster analysis and the analysis of similarity ANOSIM. We collected 1721 individuals belonging to 58 species in Ubatuba beach. Trachinotus carolinus, Diapterus rhombeus, Anchoa tricolor, Anchoa januaria and Oligoplites saliens were the most abundant species. On the other hand, in Caraguá beach were captured 1228 fishes distributed in 59 species. Oligoplites saliens, Chloroscombrus chrysurus, Larimus breviceps, Trachinotus carolinus, Genidens genidens and Harengula clupeola were the most abundant species. Significant differences were observed between beaches to number of individuals and diversity. Additionally, richness and diversity also differed seasonally. Cluster analysis separated the fish assemblages in space and time, with the presence of two groups: spring/summer and autumn/winter. The ANOSIM demonstrated that the compositions of the assemblies of both beaches are different. The ABC curves confirmed the unsettle status for both beaches allowing to infer that the organic load factor, commonly dumped in these environments, could influence the assemblies structure. The null hypothesis was rejected due to differences between fish assemblies, confirmed by analyzes set used.