A year-long beach seine survey at the continental margin of Sepetiba Bay, Rio de Janeiro State, Brazil, catching mainly young-of-the-year and juvenile fishes was carried out from July 1983 to June 1984, in order to describe the community structure and their spatial and seasonal variations. Fifty-five monthly samplied carried out in five sites in the marginal surf zone waters yielded 11,463 fishes in 82 species, 59 genera and 31 families. Gerreidae, Engraulidi-dae, Atherinidae and Ariidae families amounted 87.01% of the total catch in number, and 81% in weight. Cerres aprion Cuvier, 1829, Anchoa januaria (Steindachner, 1879), Anchoviella lepidentostole (Fowler, 1911), Atherinella brasiliensis (Quoy & Gaimard, 1824) and Neluma barba (Lacépède, 1803) were the most numerous species, each one contributing more the 4% of total catch. Overall, both spatial and seasonal changes in fish were not evident although most individuais were more abundant in the outer Bay. The high number of fish species in this area, suggest the important role played by the Sepetiba Bay in the fish community to where many species probably migrate from the nearby sea and stay in the Bay during part of their life cycle. Decreasing diversity and high dominance of a few number of species seem to indicated a trend of environmental deterioration in the Sepetiba Bay over the last decade, as this date are compared whith similar sampling program carried out in 1993/94. It same to indicated that changes in fish populations which use this area as rearing grounds, occurred during their early life history.
Sepetiba Bay; ichthyofauna; fish; bioecology