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We examined the changes in composition of fish assemblages for all seasons in the Rio de la Plata estuary (36°S, 56°W), and identified the parameters that control the main structuring of the estuarine community. Multivariate analysis (DCCA), performed on species biomass (t nm −2 ), indicated a spatial structuring of the estuarine community in three areas: inner, central and outer. Bottom salinity was the main factor associated with the significant differences in species composition. Examination of the estuary as a whole indicated a persistent spatial pattern, and suggested that temperature has the strongest influence on seasonal structure of fish assemblages. Both seasonal migrations (for example, of Trichiurus lepturus and Discopyge tschudii ) and reproductive movements (for example, of Micropogonias furnieri , Mustelus schmitti and Cynoscion guatucupa ), appear as important factors affecting the temporal structure of the estuarine community. |
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