Structure and dynamics of distinct fish assemblages in three reaches (upper,middle and lower) of an open tropical estuary in Brazil |
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| Authors: | Leonardo M Neves Tatiana P Teixeira Francisco G Araújo |
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| Institution: | Programa de Pós Gradua??o em Biologia Animal – PPGBA, Universidade Federal Rural do Rio de Janeiro, Laboratório de Ecologia de Peixes, IB/DBA, Seropédica, RJ, Brazil |
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| Abstract: | We collected fishes and environmental variables in three zones (upper, middle and lower) of a small open tropical estuary during flood tide. The aim was to test for differences in fish assemblages along a gradient from freshwater to marine waters and to detect any seasonal variation in fishes and environmental variables across these zones. A total of 111 species (18 in the upper, 50 in the middle and 66 in the lower estuary) were recorded, forming three distinct fish assemblages, with the family Eleotridae dominating in the upper, Gerreidae in the middle, and Sciaenidae in the lower estuary. Only two species (Geophagus brasiliensis in the upper and the middle zones, and Eucinostomus argenteus in the middle and the lower zones) composed more than 1% of the total number of individuals in more than a single zone. Short‐term (tidal) changes in salinity in the middle estuary were associated with different assemblages in the three estuarine zones, even in winter, when the differences in salinity are lowest between the middle and the lower zones. Seasonal variation in salinity was irrelevant, except in a protected sidewater lagoon in the middle estuary. Low salinity seasonal change may be related to the lack of seasonal variation in the structure of fish assemblages in all estuarine zones. |
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| Keywords: | Environmental variables estuaries fish assemblages habitat structure salinity gradient |
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