Spatial and seasonal variation of the ichthyofauna and habitat use in the inner portion of the Brazilian Amazon estuary

Abstract

It was analyzed the diversity of the ichthyofauna in the inner portion of the Amazon Estuary, its spatial and temporal distribution and abundance considering the salinity gradient and the importance of the area as reproduction and nursery grounds. Data were obtained in Guajará and Marajó Bays, and in Guamá River. Specimens were captured in the main channel (gillnets and trawl nets) and tidal creeks (block nets) between 2004 and 2011 during the dry (July-December) and rainy seasons (January-June). A total of 41,516 specimens of 136 taxa were analyzed . Differential fish composition, abundance and use of the zones as nursery and breeding area were observed, driven mainly by the salinity. The main river channel of Marajó Bay returned the highest values of abundance, especially during the dry season. The tidal creeks were used more frequently as reproduction area than the main river channels. Small-sized fishes predominated in all zones. Total species richness (S), diversity and abundance (main river channel) was highest in Marajó Bay and lowest in Guamá River (richness) and Guajará Bay (Margalef’s D and Shannon’s H’). The most species, especially in Guajará and Marajó Bays, were occasional and accessory, characterizing the study area as a transitional zone, with the presence of freshwater, estuarine and marine species in all stages of the life history. The systematic monitoring of the area should have the highest priority, considering the importance of this area in terms of biodiversity and as a source of income and subsistence for local populations.