Factors Affecting Rearing of Settled Zebra Mussels in a Controlled Flow-Through System

Abstract The growth of the settled zebra mussel Dreissena polymorpha was analyzed in a controlled flow-through system with fresh unicellular alga Selenastrum capricornutum as the food. Stocks of live algae from a light-regulated chemostat were diluted and metered continuously into rearing tanks that contained the mussels. Growth and migration of the mussels inside the tank were recorded over a 3-month period. Small mussels (1–3 mm) migrated frequently and had a high mortality rate (>99%). The mortality rate of the larger mussels (>12 mm) was lower (25%). Larger size mussels seldom migrated, but they did not increase in size during the entire 3-month period. Medium-size mussels (3–12 mm) exhibited strong photophobic behavior. Significant growth was observed in individuals that settled in dim places away from rapid water current. Results suggested that illumination should be examined as a potential detererent to the settling of this organism.