Grass Carp: A Fish for Biological Management of Hydrilla and Other Aquatic Weeds in Florida

Abundant growth of aquatic plants causes serious problems in ponds, lakes, rivers, and irrigation and drainage throughout Florida. In some situations, native aquatic plants become weeds, but most often exotic plants introduced from areas outside the state flourish under the favorable growing conditions found in Florida. Long-term economical solutions to Florida's aquatic weed problems have been elusive and there is a need for control techniques to alleviate aquatic weed problems. This bulletin provides information on a biological method, the grass carp (Ctenopharyngodon idella Val.), for management of some of Florida's aquatic weed problems. Emphasis is placed on use of this fish to control hydrilla (Hydrilla verticillata [L.f.] Royle) and other submersed aquatic plants. Since the grass carp is a living organism - in contrast to either herbicides or mechanical devices used for aquatic weed management a somewhat different approach is required. A knowledge of the life cycles of plants that become weeds and feeding behavior of the fish are important considerations in understanding the various ways in which grass carp can be used to manage plant problems. The grass carp will not be useful for all aquatic plant problems; rather it offers the potential to effectively and economically manage certain of them. Man has probably been the single most important