Some Effects of Suction Dredge Placer Mining on the Short-term Survival of Freshwater Mussels in Washington

Suction dredge placer mining is an increasingly frequent activity that may affect the survival of mussels, however, the effect of suction dredge mining on freshwater mussels has received little attention. We quantified the effects of being entrained, exposed, and/or buried by suction dredge placer mining on the short-term survival of western ridged mussels (Gonidea angulata, Lea) and western pearlshell mussels (Margaritifera falcata, Gould) in the Similkameen River, Washington. The primary experimental treatments were entrainment by a suction dredge versus non-entrainment. The secondary experimental treatments were exposure and burial. No obvious physical damage to mussels was observed due to entrainment by the suction dredge and entrainment had no effect on the survival of mussels. All exposed mussels survived the 6-week experiment. However, burial by dredge tailings resulted in the death of a substantial percentage of mussels of each species and no mussels were able to excavate from experimental dredge tailings. Our results have significant conservation implications and emphasize the need for additional research.