Diet of Ctenogobius shufeldti (Jordan and Eigenmann, 1887) (Teleostei, Gobiidae) in Guaratuba Bay, subtropical west Atlantic

The diet composition of the American freshwater goby, Ctenogobius shufeldti, was investigated in an estuarine area and two of its tributaries. 397 individuals, total length from 21 to 70mm, were sampled over a period of 12 months and their stomach contents were analysed by the Frequency of Occurrence and Number of Points methods. According to the Alimentary Index, diet was constituted mainly by Ostracoda (IA=50.51) and Tanaidacea (IA=40.85), and secondarily by Gastropoda (IA=1.21), Amphipoda (IA=0.10), Isopoda (IA=0.01), Cirripedia (IA=0.01), Decapoda larvae (IA=0.01), Insecta (IA=0.01), Chlorophyta (IA=2.15) and Rodophyta (IA=0.15) filamentous algae, and plants (IA=4.99). Diversity of diet was higher in rivers than in the Bay. Except for Decapoda larvae, items found in the two rivers were the same. In the Bay, Amphipoda and Cirripedia were not found. Previous to this research, the filamentous algae Chlorophyta and Rodophyta had not been noted in the diet of this species in estuaries close to Guaratuba. In view of this, and regarding the possible roles played by cryptobenthic fish species in aquatic communities (Depczynski and Bellwood, 2003), it is concluded that C. shufeldti takes part in trophic dynamics feeding on benthic organisms as well as on algae, a behaviour that can result from both marine and continental influences existing in the region