There are three species of mussels in the Tualatin River (Western Pearlshell, Floater and Western Ridged). Western Pearlshell and Floater Mussels are relatively common. It is known via DNA sampling of the river water that Western Ridged Mussels are in the Tualatin River, but their exact location is currently unknown. These mussels have a very interesting life cycle which includes a larva stage that attaches to fish gills enabling the mussels to propagate upriver.
Freshwater mussels are sensitive to water pollution and habitat changes. Over 75% of the freshwater mussels in North America are listed as endangered, threatened or of special concern. A petition to add the Western Ridged Mussel to the Endangered Species List is currently being reviewed by US Fish & Wildlife.
