Trophic interactions between fish and other compartment communities in a tropical estuary in Brazil as indicator of environmental quality

Studies on fish stomach contents were carried out to assess the trophic interactions between them and other compartment communities of the Santa Cruz Channel, a tropical estuary in Brazil. Food items quality and quantity were used as a valuable tool to assess the environmental quality. The study was based on samples collected from 1995 to 1998, besides published data since 1979. Groups interactions were based on food items of 27 fish species. The Sorensen similarity index was used for cluster analysis. Many different taxa appeared in fish stomachs and there was considerable spatial and temporal variation in food eaten even for the same species. Many related food groups were registered, among which two could be considered the most important: those formed mainly by microalgae, sponges and detritus; and the other by molluscs, crustaceans, nematodes, annelids and fish. Because many fish fed from benthic and pelagic pathways they were the main organisms that linked the benthic and pelagic energy flow. The results reveal that the Santa Cruz Channel, despite human impacts, is still an ecosystem capable of supporting fish populations.