The role of zooplankton in the feeding ecology of fish fry from some southern African estuaries

The stomach contents of more than 1000 fish fry (< 30 mm S.L.) comprising 11 species, were examined from the Mhlanga and Swartvlei estuarine systems. Calanoid and cyclopoid copepods were the dominant food item of fry < 20 mm S.L., with the exception of Diplodus sargus and Sarpa salpa where harpacticoid copepods were the main invertebrate prey. Although the diet of fry <20 mm S.L. varied according to the availability of different foods, zooplankton was the major prey category for this size class of fishes in estuaries with both low and high zooplankton biomasses. The advantages of feeding on zooplankton by estuarine fry and possible reasons for ontogenetic changes in diet are discussed