Feeding ecology of major carnivorous fish from four eastern Cape estuaries

Abstract

Stomach content analyses were performed on eight carnivorous fish from four eastern Cape estuaries. Dietary importance was assessed by using three unrelated methods and by combining them to determine the index of relative importance of each food item. It was attempted to relate the percentage of fish with food in the stomach and the feeding intensity to the abundance of the fish in a particular estuary. In general fish consumed more food in estuaries where they were more abundant. The few exceptions that occurred could indicate that a particular estuary was selected for purposes other than food availability eg. Tachysurus feliceps in the Krom estuary for spawning grounds or because of inter- or intraspecific competition for food eg. T. feliceps and Monodactylus falciform is in the Krom and Argyrosomus hololepidotus in the Gamtoos and Sundays estuaries. Similarity analyses showed resource partitioning. Predators such as A. hololepidotus, Elops machnata, Lichia amia and Platycephalus indicus preferred teleost fishes such as mullets and Gilchristella aestuarius, whereas the stomach content of Pomadasys commersonnl, T. feliceps and M. falciform is were dominated by Crustacea, particularly Upogebia africana. Most estuarine predators showed a diverse prey selection, but the food web was characterized by a high energy flow per pathway.