Since the spread of common carp into South Australia in the early 1970's, they have remained abundant in the River Murray and the lower lakes. With the continued high catch rates, there has been concern as to the effects carp may have on the environment and on native fish. This impact will be determined largely by the feeding habits of carp. Although carp are recognized as the most widely distributed freshwater fish, very little is known of their ecology in natural environments. overseas studies have suggested that carp feed by 'roiling' the mud and selecting food particles from the suspended matter. This study aimed to determine the diet of carp in Lake Alexandrina and to make inferences on the environmental effects carp may produce.