Macrophyte Control by Grass Carp in Catfish Ponds

Macrophyte standing crop (primarily Eleocharis and Utricularia) was reduced nearly 90% in two catfish ponds after introduction of grass carp (Ctenopharyngodon idella). Abundant vegetation remained in 1-m2 exclosures placed in the ponds as controls. The stocking ratio of grass carp (live weight) to macrophyte standing crop (dry weight) that resulted in vegetation control within 1 year was 0.15 in the pond is which the fish were fed pelleted food and 0.06 in the pond in which the flsh were not fed. Scattering of feed over the entire pond rather than conflning it to a few locations may have discouraged grass carp from feeding on pellets and contributed to the success of vegetation control.