The food and feeding ecology of Gerreidae, Bleeker 1859, in the estuaries of Natal

The food and feeding ecology of five species of Genes in the estuaries of Natal, were investigated from 1978 to 1980. The Kosi system, consisting of an estuary and three main lakes was selected as the main study area due to an abundance of Genes . Four other estuarine systems were sampled. At Kosi polychaetes were important at the estuary, siphon tips (distal ±5 mm) of the bivalve Hiatula lunulata were most commonly taken in Lakes Makhawulani and Mpungwini, while chironomid larvae were important in Lake Nhlange. Ivlev's electivity test showed that Genes positively selected bivalve siphon tips when searching for food. The food taken by Genes from other estuaries was similar to that at Kosi, although the proportions of the different prey varied. At Kosi between three and five species occurred sympatri‐cally. Resource segregation was through differences in diet and feeding periodicity and a superabundance of food ( H. lunulata siphon tips) during summer and autumn. During winter and spring when food may be limiting, most Genes leave shelf areas of the Kosi system, only G. acinaces remains in large numbers. Little is known of the diet of other fish which feed on benthic invertebrates in Kosi but there is probably little direct competition with Gerreidae, although Acanthopagrus berda and Pomadasys commersonni have been recorded feeding on the siphons of the bivalve Solen corneus , the former in Durban Bay and the latter at Kosi. In areas where the bivalve H. lunulata occurs it is suggested that Gerreidae have developed optimal foraging techniques which enhance resource partitioning.