Feeding ecology of fish in a coastal river of the Atlantic Rain Forest

Feeding ecology of fish assemblage in a costal river of the Atlantic Rain Forest in Southern Brazil was investigated. Monthly samples using different fishing techniques were completed on a section of the river characterized as a freshwater environment, and an adjacent tide-influenced estuarine section. Species were grouped into three major Feeding Mode Functional Groups: Zoobenthivore, Omnivore and Detritivore. The river section with the greatest occurrence was the site where the most abundant species are likely to feed most intensively. Freshwater strangler species (Cyphocharax santacatarinae - detritivorous, Rhamdia quelen and Oligosarcus hepsetus - zoobenthivorous) presented higher stomach repletion in the freshwater environment while marine migrants (Genidens genidens and Etropus crossotus - zoobenthivorous) and estuarine residents (Bairdiella ronchus - zoobenthivorous) presented higher repletion in the tide-influenced estuarine stretch. Use of food resources was influenced by spatial and temporal variations linked to environmental characteristics such as salinity, habitat heterogeneity, life history evolution, feeding specialization and resource partitioning. Hypotheses concerning potential keystone species, ecosystem engineers or strong interactors were also discussed.