Survivorship of aerially-exposed zebra mussels (Dreissena polymorpha) under laboratory conditions

Zebra mussels (Dreissena polymorpha) were aerially exposed at temperatures of 5 C and 20 C for 12, 24, 36, and 60 h. Survivorship was nearly 100% in a ll control containers and for the 5 C replicates but declined substantially in the 20 C replicates after 36 and 60 h. Additional zebra mussels were ae rially exposed at 5 C and 20 C on both wet and dry substrates for 60 h. Tho se aerially exposed on a wet substrate at 5 C had greater survivorship than did mussels on a dry substrate at 20 C. Larger zebra mussels (shell length > 16 mm) were significantly more likely to survive exposure for 36 or 60 h at 20 C than were smaller individuals. These results show that survivorshi p of freshly-collected zebra mussels under controlled, biologically-relevan t conditions is strongly affected by length of aerial exposure, ambient tem perature, substrate moisture, and mussel size. Our findings largely confirm results of companion field experiments, implying that temperature and mois ture conditions caused the observed zebra mussel mortality in nature. Taken together, these studies suggest that aerial exposure at warm temperatures (greater than or equal to 20 C) may be an effective control for zebra musse ls in regulated waters where water levels can be lowered for more than 24 h .