Consumption and growth of hybrid grass carp fed four vegetation diets and trout chow in circular tanks

Grass carp, Ctenopharyngodon idella, and hybrid grass carp (grass carp ♀× bighead carp ♀Aristichthys nobilis), were fed duckweed (Lemna sp.), hydrilla (Hydrilla verticillata), chara (Chara sp.), filamentous algae (Odogonium sp., Spirogyra sp.), and trout chow. Grass carp consumed all plants in greater amounts than hybrids. Grass carp grew best when fed hydrilla and trout chow and showed positive growth on all diets. Hybrids grew equal to grass carp when fed trout chow but did not grow on the vegetation diets. Low consumption rates of aquatic plants may indicate that hybrids are questionable as a plant biocontrol agent.