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Community structure of the demersal fish of Sepetiba Bay, RJA year-long otter trawl survey in the Sepetiba Bay, Rio de Janeiro State, Brazil, was carried out in order to describe the fish community structure and their spatial and seasonal variations. Sampling carried out between July 1993 and June 1994, yielded 97 species, 70 genera and 38 families. Ariidae, Gerreidae, Sciaenidae, Carangidae and Sparidae families amounted 69,9% of the total catch in number, and Ariidae, Sparidae, Gerreidae, Haemulidae and Sciaenidae amounted 67,9% of the total weight. Genidens genidens, Gerres aprion, Cathorops spixii, Micropogonias furnieri and Chloroscombrus chrysurus were the most numerous species, each one contributing more than 5% of the total catches. Higher numbers of fishes were associated with low depths and transparencies of the inner Bay, while salinity is a quite stable environmental parameter ranging around 29%o most of the time all over the Bay. Numbers of fish are higher in Late Summer and Early Winter. Overall, most number and weight of fishes were higher in the inner Bay than in the outer area next to the sea limit, while the number of species was higher in the outer Bay. The high number of fish species suggests the important role played by the Sepetiba Bay as rearing and residence grounds for the fish community.Key words: Sepetiba Bay, ichthyofauna, coastal lagoons, fish, community. RESUMOUm programa de amostragens mensais de arrasto de fundo em sete estações de coleta na Baía de Sepetiba foi realizado entre julho de 1993 e junho de 1994 com o objetivo de descrever a estrutura da comunidade de peixes e suas variações espaciais e temporais. Noventa e sete espécies de peixes foram levantadas, compreendendo 70 gêneros e 38 famílias. As famílias Ariidae, Gerreidae, Sciaenidae, Carangidae e Sparidae, nesta ordem, foram as mais abundantes em número, contribuindo com 69,9% do total capturado, enquanto Ariidae, Sparidae, Gerreidae, Haemulidae e Sciaenidae somaram 67,9% do peso total. Genidens genidens, Gerres aprion, Cathorops spixii, Micropogonias furnieri e Chloroscombrus chrysurus, nesta ordem, foram as espécies mais abundantes, contribuindo cada uma com mais de 5% do número total de peixes capturados. O maior número de peixes foi associado às menores profundidades e transparências, enquanto a salinidade apresentou, na maior parte do tempo, valores estáveis em torno de 29%o. Maiores abundâncias de peixes ocorreram entre fins do verão e início do inverno. O número e peso dos peixes foram maiores na zona interna da Baía enquanto

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ABSTRACT. Spatial and seasonal variations in community fish structu re of juvenile fish in Sepeliba Bay, Rio de Janeiro. A year-Iong beach seine survey at the continental margin of Sepetiba Bay, Rio de Janeiro State, Brazil, catching mainly young-of-the-year andjuvenile 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 oul in tive sites in the marginal surfzone waters yielded 11,463 fishes in 82 species, 59 genera and 31 families. Gerreidae, Engraulididae, Atherinidae and Ariidae families amounted 87.01 % ofthe total catch in number, and 81 % in weighl. Gerres aprion Cuvier, 1829, Anchoa januaria (Steindachner, 1879), Anchoviella lepidentostole (Fowler, 1911), Atherinella brasiliensis (Quoy & Gaimard, 1824) and Netuma barba (Lacépede, 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 cyc1e. 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 simi lar sampling program carried out in 1993/94. It sarne to indicated that changes in fish populations which use this area as rearing grounds, occurred during their eariy life history.

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ABSTRACT. Reproductive biology of the marine catfish Genidens genidensValenciennes and Cal"orops spixii Agassiz (Siluriformes, Ari idae) in the Sepetiba Bay, Rio de Ja neiro, Brazil. The reproductive cycle ofthe marine catfishes Genidens genidens Valenciennes, 1833 and Calhorops spixii Agassiz, 1839 in the Sepetiba Bay, was assessed by an annual period of sampling from October 1993 to September 1994. The fishes were caught by standardized otter trawl and environmental parameters of tel11perature, salinity and transparency ofwater were recorded at each sampling. Five gonadal phases were described, based in macroscopic observations. Changes in the gonadosomatic index (GS1) and in the percentual of stages of gonadal development showed that G. genidens spawns in Summer/early Autul11n, coinciding with low salinity and high temperature and transparency. Calhorops spixii spawns in late Spring/early Summer, coinciding with rising temperature and transparency and low salinity. Total spawning are shown for both species, as indicated by length-trequency of oocytes per stages of l11aturation with two groups synchronic development of oocytes. Fecundity is low (10-23 oocytes, for G. genidens and 24-30 for C. spixii), when compared with other teleosteans, and was not strongly correlated to the total length (G. genidens, r=0.65, C. spixii, r=0.76). Strategy-k is developed by both species as indicated by high brood and enbrions protection and high body length. KEY WORDS . Siluriformes, Ariidae, reproduction, Marine Cattish, Sepetiba Bay Os bagres marinhos pertencentes à família Ariidae ocorrem em zonas litorâneas sendo geralmente mais abundantes em águas costeiras pouco profundas, em fundo lodoso ou arenoso (.ARAúJO 1988; ANDREATA et aI. 1989). São considerados como recursos de grande importância econômica na pesca artesanal, principalmente na região sul (REIS I 986a). Na época da desova, procuram a desembocadura dos rios e regiões lagunares realizando incubação oral com machos e raramente as fêmeas, carregando ovos e formas iniciais da prole até completarem o desenvolvimento embrionário (Y ANEZ-ARANCIBIA & SANCHEZ-GIL 1988;REIS 1986b).A biologia reprodutiva deste grupo de peixes é pouco estudada na costa do Brasil e isto faz com que especial interesse seja direcionado para as espéciesGenidens genidens e Cathorops spixii devido sua grande distribu ição em estuários