Field Testing of Protocols to Prevent the Spread of Zebra Mussels Dreissena polymorpha during Fish Hatchery and Aquaculture Activities

Abstract

The zebra mussel Dreissena polymorpha, an introduced, aquatic bivalve species, causes changes in the ecology and negatively impacts the economic value of infected water bodies. Unfortunately, the spread of the zebra mussel can be facilitated by aquaculture activities. We field-tested the effectiveness of chemical treatment protocols established to prevent the spread of microscopic zebra mussel larvae (veligers) during fish stocking. We achieved more realistic exposure conditions by performing fish and veliger toxicity tests in aerated 750-L tanks on fish hatchery tanker trucks using the chemical treatments established in earlier laboratory work. Posttreatment survival was measured for veligers in the 750-L tanks, followed by an assessment of the survival of walleye Stizostedion vitreum and saugeye (sauger S. canadense × walleye) 5 d after stocking into 4,000-m² fish ponds. A 1-h pretreatment of 750 mg/L KCl followed by a 2-hr treatment of 25 mg/L formalin was effective in killing veligers without causing fish mortality. However, the addition of 0.5% NaCl to alleviate transport stress in fish did not increase fish survival and left many veligers alive.