Trophic organization and functioning of fish populations in the Bay of Guaratuba, Brazil, on the basis of a trophic contribution factor

Abstract

          Trophic organization and seasonal development in the Bay of Guaratuba (Brazil) are characterized, based on feeding habits of fish species taken from the literature and on a factor that combines biomass and species richness to determine to what extent detritus and primary production contribute to the trophic network. The Bay of Guaratuba contains all trophic categories of fish: herbivores, plankton-eaters, consumers of invertebrates with occasional supplementation of plants and fish, and fish-eaters. Resident and migrant species occupy different trophic ranges, depending on whether their food sources are available on a permanent or seasonal basis. Residents tend to feed on benthic invertebrate meiofauna and macrofauna, using relatively more detritus than primary production sources. Migrants time their presence in the bay with seasonal productivity, especially of plants. Most occasional visitors consume invertebrates plus fish or primarily fish. The fish-eaters could explain the lower number of fish in this estuary in winter. The Trophic Contribution Factor is a useful tool for characterizing the input of basic elements to the trophic network, monitoring how the occupancy status of species affects their time-space variations, and comparing different localities and ecosystems.