Seasonal changes in density, biomass, and diversity of estuarine fishes in tidal mangrove creeks of the lower Caeté Estuary (northern Brazilian coast, east Amazon)

Abstract

The present study investigated the assemblage of fish species in an intertidal mangrove forest during high tide in a macrotide region. We describe the seasonal changes in the fish assemblage composition in relation to biomass, density, and species number in tidal creeks of the Furo do Meio, Caete Estuary, Brazil. A total of 29 107 individuals of 49 species in 26 families were caught using a block net. Their total weight was 526 kg (total density 0.11 ind. m -2 and total biomass 2.1 g m -2 ). Analysis of the catch data showed that the number of species varied significantly between creeks, and that total fish biomass differed significantly between seasons. The densities and biomass of the 2 most important species, Cathorops pleurops and Colomesus psittacus, were significantly different between seasons. The densities and biomass of C. pleurops, Pterengraulis atherinoides, Pseudauchnipterus nodosus, and Stellifer naso showed significant temporal differences. Significant differences between creeks were observed in the density and biomass of Anchovia clupeoides and Rhinosardinia amazonica. The abundance-biomass comparison (ABC) plots for the fish fauna in the creeks of the Furo do Meio showed that the dominant species increased in number and weight at the beginning of the rainy season. As a result of increased rainfall in March and April, salinity declined to values between 6 and 8 psu. At that time, the dominant species made up more than 60% of the total biomass and density and Hill's index of diversity (N1) declined, whereas the number of species (NO) and evenness (E2) did not change. After April, rainfall decreased, and density and biomass returned to levels similar to those before the rainy season. The number of species and the density and biomass in the mangrove tidal creeks are compared with published data for other tropical and subtropical estuaries. Migration trends were inferred from the results of the seasonal fluctuations of density and biomass of the most important species in the Furo do Meio, and are compared with data from other studies in the main channel of the Caete Estuary.