ICHTHYOFAUNA FROM AN AMAZONIAN ISLAND: DIVERSITY, REPRODUCTION, AND FEEDING ASPECTS

Uses of an estuarine amazonian island by the ichthyofauna

Abstract

The high productivity in estuaries supports a high biomass of fishes, making them important environments for feeding, development, and reproduction of larvae and juveniles of many economically and ecologically important species. Many islands compose the landscape of the Amazon estuary given the large deposition of soil caused by the Amazon River waterflow. Given the importance of estuarine environments to coastal ecosystems, this study aims to diagnose the fish community inhabiting a typical island of the Amazon estuary and describe the temporal patterns in community composition, reproductive and feeding activity. Specimens were collected in the main channel and a tidal creek of Onças Island, quarterly between September 2006 and 2008, using gillnets and block-off nets. Captured fishes were identified, sexed, measured (total length and weight), had reproductive and feeding activities described, and were classified into environmental and feeding guilds. Abundance and biomass were expressed by the Capture per Unit of Effort in number of individuals (CPUEn) and biomass (CPUEb). The island was characterized as a nursery ground (high abundance of individuals with immature and at maturity gonads), reproduction ground (high abundance of individuals with mature and spawned/spent gonads) and feeding ground (high abundance of individuals with stomachs containing food). A total of 37 species distributed in 21 families and 1,177 individuals were captured. Richness varied significantly throughout the collections but there were no significant differences in fish abundance (CPUEn) or biomass (CPUEb) between periods in any habitat type. Individuals displayed different feeding activity between hydrological periods and feeding guilds. Freshwater species dominated through all collection periods and most species were zoobenthivore, piscivore, or planktivore. Our results indicated that the island serves as a feeding and reproduction ground for several freshwater fish species, possibly reflecting the importance of other islands in Amazonian estuarine systems and highlighting their importance for conservation.