Turbidity-induced changes in feeding strategies of fish in estuaries

The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commersonnii (a macrobenthivore) and Atherina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A breviceps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders