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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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Spacial and temporal variation of marines catfishes on Sepetiba Bay, RJ.Marine catfishes (Ariidae) are abundant fishery resource in the Sepetiba Bay, Rio de Janeiro State (Lat. 22º54'-23º04'S; Long. 43º34'-44º10'W), that is considered an important rearing area to a great number of juvenile fish. Artisanal fisheries are important economic activity in the region. Spatial and seasonal distribution and relative abundance of marine catfish, based on the number and weight of fish catched per sample (Catch per Unit Effort = CPUE) were assessed based on 151 otter trawl sampling in seven sampling sites in the Sepetiba Bay, between July 1993 and June 1996. For spatial comparisons, the study area was devised in an inner zone, located in the inner Bay and an outer zone, near to the sea limit. Environmental parameters of surface and bottom water temperature and salinity, transparency and depth were recorded at each sampling. A spatial variation pattern, assessed by multivariate methods, is shown with higher depths and transparencies in the outer bay and lower in the inner bay, while salinity seems to decrease slightly toward the inner bay. Only temperature showed seasonal variation. Five marine catfish species were recorded in the following order of decreasing numerical abundance: Genidens genidens (Valenciennes, 1839), Cathorops spixii (Agassiz, 1829) Sciadeichthys luniscutis (Valenciennes, 1840), Netuma barba (Lacepéde, 1803) and Bagre marinus (Mitchill, 1814).The top four abundant marine catfish occur in higher abundance in the inner Bay, with indication of spatial separation within this area. G. genidens was abundant over all sampling sites in the inner Bay, while C. spixii showed a narrower distribution in this area. N. barba concentrated near to Guandú River estuary, and S. luniscutis showed an ample distribution over all the Bay. Seasonally was not marked for all species. Strategies of spatial separation may be explaining the coexistence of marine catfish in high abundance in the Sepetiba Bay, which is used as fish rearing area mainly due the low depths and transparencies, favorable conditions to their early life cycle development.

We compared fish community structure in Guaratiba Mangrove, SE Brazil, among three seasons of the hydrological cycle [(i) spring, increasing temperature and rainfall, decreasing salinity; (ii) summer/early fall, high temperature and rainfall, intermediate salinity; (iii) late fall/winter, low temperature and rainfall, high salinity] and between the years 2002–2003 and 2008–2009. The aim was to test the hypothesis that the fish community structure changes seasonally, associated with seasonal changes in environmental conditions, and that changes occurred between the two yearly periods because of increased anthropogenic activities. The sampling protocol for the two surveys was identical. A total of 63 species was recorded, with 38 species occurring in 2002–2003, and 53 species in 2008–2009. The main changes in the mangrove's fish assemblage between 2002–2003 and 2008–2009 were (i) an increase in species richness, fish density and total biomass; and (ii) an increase in the zoobenthivorous species of gerreids Eucinostomus argenteus, Diapterus rhombeus and Ulaema lefroyi, and a decrease in the planktivorous clupeid Harengula clupeola. Other abundant species, such as the opportunistic atherinopsid. Atherinella brasiliensis, the detritivorous mullet Mugil liza and the zoobenthivorous pufferfish Sphoeroides testudineus did not differ in abundance between the two yearly periods. Ten species occurred only in 2002–2003, and 23 species only in 2008–2009, indicating significant changes in community structure over the 6‐year period. Seasonal changes in community structure were more conspicuous in 2008–2009, when species abundance and richness were greatest. The highest fish abundance was recorded in spring and in summer/early fall, and the lowest in late fall/winter. The increased abundance and richness over time may be at least partially attributable to protection policies because of the effective implementation of a biological reserve in the area.