Western Pearlshell Mussel

Mussel 2

These mussels can live 100 years and have been found in the Little Pend Oreille River on the Refuge.


The western pearlshell mussel is a moderately sized mussel that can reach 4.5 inches in length; their shell is dark in color. These interesting little clam-like creatures were once thought to be the most common freshwater mussel in the northwest. Their numbers have plummeted throughout most of their range in the last couple of decades. Pearlshell mussels are dependent on clear, cold, clean water for their survival.

They have a life history typical of most mussel species. Eggs hatch into microscopic larva known as glochidia. The larva swim around until they are able to attach to the gills of fish. Once attached, they are filter feeders and strain organic material from the water. This is why they are so sensitive to water quality. They ingest everything that is in the water. After a period of a few weeks, they drop off and find a sandy stream bottom to burrow into and mature into adults.

Typical life span is around 70 years but some individuals are over 100 years old. They may only move a couple of yards for the rest of their lives. The mussels found in the Little Pend Oreille River are mostly small populations with the largest group being about 250 animals.