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Western Pearlshell mussels in Bear Creek mussel study
freshwater mussel facts
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The United States boasts the largest number of mussel species in the world at almost 300 different kinds. Most species are found east of the Mississippi River. Washington has only 6 species.
Most mussels live burrowed in gravel and sand at the bottom of rivers or lakes. These sedentary creatures get their food by filtering water and ingesting plankton. While siphoning the water they also filter out impurities and process nutrients for other stream critters while helping stabilize the streambed.
Reproduction occurs during spring and early summer where the male releases sperm into the water. The female may produce thousands of eggs. The eggs brood in the gills until they turn into glochidia (the larval stage). They are then expelled into the water where they must find a specific host fish (salmonids in this region) to attach to. To increase the chance that the glochidia find a fish, the larvae may be encased in a membrane that mimics food the salmon eat. When the fish gets close, the membrane will explode open like a dried seedpod and the larvae will attached themselves to the host fish. After a few weeks, when the larvae develop into juveniles they drop off the fish and begin life in the stream bottom. Smaller mussels live in the shoreline area and larger adults live in the main channels. They may be seen partially buried vertically in the streambed or laying flat on top of the substrate. They can live up to 100 years.
They are known to have been part of our regional streams for at least 2000 years. Archeological sites indicate that they were a food source for indigenous tribes which left “mussel middens” at streamside campsites. Mussels used to be in most streams in Puget Sound, but urbanization has destroyed most populations.
These small creatures may be the most troubled species in this country. Nearly 70% of our freshwater mussels are extinct or endangered. Pollution is the greatest threat to native mussels. Also causing their demise is sedimentation, clearing of riparian and streambank vegetation, habitat loss, loss of host fish and urbanization pressures. Mussels are very sensitive to changes in water quality, making them an excellent indicator species . Dead mussels may indicate serious pollution or other environmental problems. Large amounts of live mussels indicate clean healthy water.
The Bear Creek Watershed has a very large concentration of fresh water mussels. The Western Pearlshell (Margaritifera falcata) is the most abundant mussel found in our watershed, yet the population is in trouble. There are large sections of our streams where many dead mussels will be found. It is a cause for concern. To find out just what is happening, Water Tenders has funded, for the past three years, a study to ascertain the cause of these die-offs. These studies are posted on our website for your perusal. Studies will continue as no cause has yet to be determined.
 
OCTOBER 1
MEET THE SALMON, 1-4pm, at junction of Bear Creek and Tolt Pipeline off Mink Rd.
OCTOBER 6
MEET THE SALMON, 3-6pm, at junction of Bear Creek and Tolt Pipeline off Mink Rd.
OCTOBER 8
MEET THE SALMON, 1-4pm, at junction of Bear Creek and Tolt Pipeline off Mink Rd.
OCTOBER 15
Cold Creek Nature Preserve restoration project. Plant native shrubs. Park at Mary Cash Farm Park and walk gravel road to site. Rain or shine.
NOVEMBER 12
ADOPT-A-PARK 9am-noon, Clean various open space parks in Upper Bear Creek area. Meet at Mary Cash Farm Park.
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