by Joe Bartoszek, Ph.D., Resource Contaminant Specialist, Washington Fish and Wildlife Office
When people in Washington think of mussels, they usually conjure up thoughts of tasty coastal shellfish dripping with butter. But mussels are also found in fresh water. In fact, North America has the largest number of species of fresh water mussels found anywhere in the world--nearly 300 species, or about 35% of the world’s varieties! Freshwater mussels are also among the most imperiled animals in North America.
Most of North America’s freshwater mussel species are in the southeast (Alabama has 180) but in eastern Washington we have about 5 species . Two species that used to be found in the Hanford Reach are the western pearlshell (Margaritifera falcata) and western ridged (Gonidea angulata). Middens (piles of old shells) containing western pearlshell have been found along the Hanford Reach. Some of these old shells were left there as long as 6,000 years ago. From evidence like this, we assume that the western pearlshell has long been an important resource in the Columbia River and in particular the Hanford Reach.
Although a 2004 survey of the mussels at Hanford Reach did not turn up any live western pearlshell, a shell of a recently dead (within the last 10 years) western pearlshell WAS found. Hanford Reach still appears to be suitable habitat for the western pearlshell. So why are they no longer found there? Can it be related to the presence of the Hanford Nuclear Reservation? If so, what could have caused them to disappear? Can they be brought back successfully? These are some of the questions the Fish and Wildlife Service are hoping to be able to answer with a study we began with the Hanford Natural Resource Trustees to look at the toxicity of hexavalent chromium, a Hanford Site contaminant, to the western pearlshell.
Stay tuned for further Word from the Wild installments as we uncover some of the mysteries associated with this complex and unusual creature.
|Western pearlshell mussel|
Photo credit: M. Fernandez, USFWS