Nutritional Implications of Surface Feeding by Gizzard Shad (Dorosoma cepedianum) on Insect Remains in an Ohio Reservoir

On six occasions during July and August 1975, surface feeding by schools of adult gizzard shad (Dorosoma cepedianum) on insect remains was observed in Acton Lake, Ohio. Proteinases in the digestive tract presumably hydrolyze the protein in the insect cuticle. The chitin component of the cuticle also has nutritive value, as significant chitinase activity was demonstrated in extracts of gizzard mucosa, hepatopancreas, and intestinal ceca. Values were comparable to activities observed in other fish species. Chitinolytic system activity was not demonstrated.The mean caloric equivalents of the chironomid and chaoborid exuviae and winged ants in surface debris were 5355, 4363, and 6059 cal/g ash-free dry wt, respectively. Ingestion of insect remains by this forage species could accelerate the return of energy and nutrients in these materials to higher trophic levels.