Transplants of western pearlshell mussels to unoccupied streams on Willapa National Wildlife Refuge, southwestern Washington

Abstract

The western pearlshell mussel Margaritifera falcata is a species of freshwater mussel listed as vulnerable in the state of Washington. From 2007 to 2009, 265 western pearlshell mussels were transplanted from the Bear River to four streams within the Willapa National Wildlife Refuge in southwestern Washington. Transplanted western pearlshell mussels were monitored for survival and growth, as well as reproduction. Between 55% and 95% of the transplanted western pearlshell mussels could be accounted for in individual streams in 2010. Growth increments measured from September 2008 to March 2010 ranged up to 6.5 mm. Evidence of reproduction in western pearlshell mussels was observed in two streams. The project provided a rare opportunity to explore transplant techniques and gauge the success of these efforts for this species in the Pacific Northwest.