Ictiofauna associada às praias de desova de quelônios no baixo rio purus, amazonas, brasil

Abstract

The main goal of this work was to verify the influence of turtle hatchings over the composition of the ichthyofauna found in sand beaches with turtles nesting sites ( tabuleiro beaches Rebio Abufari) and without nesting sites (no-tabuleiro beaches RDS Piagaçu-Purus), on lower rio Purus. Samples were obtained in November of 2006 and of 2007. Data from the first field trip (2006) was used to estimate the ichthyofauna composition on these sand beaches and to evaluate fish gear selectivity. For this analysis gill-nets and seines were used. Data from the second field trip (2007) was used aiming to: 1) verify possible differences in the composition of the ichthyofauna between the two kinds of sand beaches (tabuleiro and no-tabuleiro); 2) verify possible differences in the composition of the ichthyofauna between periods (diurnal and nocturnal) on each beach; and 3) evaluate the presence of potential fish predators on turtles. A total of 146 fish species were captured belonging to 10 orders and 31 families. Gill-nets were efficient as a complementary fish gear for surveying the ichthyofauna on these beaches. There was a difference on fish assemblages composition, notably the higher number of predators at the tabuleiro beach. Richness, diversity, abundance and biomass also differed between the beaches, where the higher values were registered for the tabuleiro beach. Multiple regression analyses for abundance and biomass revealed there was difference on fish assemblages related to kind of beach and period of the day. Fish assemblages showed more similarity between day and night samples in the same beach than between night-night or dayday samples on different beaches. Stomach content analyses did not reveal any fish feeding on young turtles, however, evidences suggest that the arowana (Osteoglossum bicirrhosum) might be an important predator of young turtles. The results of this work certainly contribute to increase the knowledge of the ichthyofauna in sand beaches.