PREVENTION OF ZEBRA MUSSEL INFESTATION AND DISPERSAL DURING AQUACULTURE OPERATIONS

The zebra mussel Dreissena polymorpha, an exotic invasive species, pos es a major threat to North American fish management programs and the a quaculture industry. Fish hatcheries may become infected with zebra mu ssels from a variety of sources, including the water supply, fish ship ments, boats, and equipment. The hatcheries could then serve as agents for the overland dispersal of zebra mussels into stocked waters and t o other fish hatcheries. We evaluated the effectiveness and safety of aquaculture chemicals for use in controlling zebra mussels in fish hat cheries and preventing dispersal of veligers during fish transport. Ch emicals were evaluated for use in fish transport and as disinfectants for ponds and equipment. Standardized static toxicity tests were condu cted with representative species of warmwater, coolwater, and coldwate r fishes and with larval (3-d-old veligers), early juvenile (settling larvae), and adult zebra mussels. Chemical concentrations and exposure durations were based on recommended treatment levels for fish, eggs, and ponds. Recommended treatment levels were also exceeded, if necessa ry, to establish lethal levels for zebra mussels of different developm ental stages. Our results indicate that some chemicals currently in us e in hatcheries may be effective for controlling zebra mussels in vari ous operations. Chloride salts were the safest and most effective ther apeutants tested for use in fish transport. The toxicity of chloride s alts to fish varied among species and with temperature; only one treat ment regime (sodium chloride at 10,000 mg/L) was safe to all fish spec ies that we tested, but it was only effective on veliger and settler s tages of the zebra mussel. Effective disinfectants were benzalkonium c hloride for use on equipment and rotenone for use in ponds after fish are harvested. The regulatory status of the identified chemicals is di scussed as well as several nonchemical control alternatives.