OF ZEBRA MUSSEL (DREISSENA-POLYMORPHA) LIFE STAGES TO CANDIDATE MOLLUSCICIDES

We developed methods for measuring the toxicity of candidate molluscic ides to several life stages (preveliger, D-stage veliger, post-D stage veliger, plantigrade, and adult) of the zebra mussel Dreissena polymo rpha: Veligers were obtained by inducing ripe adults to spawn in the l aboratory and by field collection. Plantigrades were collected on slid es suspended in Lake Erie. The toxicity of candidate molluscicides on all stages was evaluated in 24 hour static tests in hard standard refe rence water. The sensitivity of zebra mussel life stages to different chemicals varied. Veliger stages showed similar sensitivity to Bayer 7 3 and TFM, whereas plantigrades and adults were less sensitive. Sensit ivity to Calgon H-130, Clamtrol CT-1, and Sal I decreased with each su ccessive developmental stage; adults were most and preveligers were le ast sensitive to rotenone. In general, chemical concentrations that ki ll adults will also be effective against other life stages. However, b ecause chemical minimization strategies require the use of the smalles t amount of chemical possible, molluscicides should be tested on the l ife stage targeted for control.