At the risk of losing incurious readers, this column begins with a brief lesson in invertebrate zoology. The topic is oysters and mussels. Stay with me. Things will get more interesting.
Oysters and mussels are classified as mollusks. A common characteristic is their two-part hinged shell, hence the term bivalves. Oysters are distinguished from mussels by having rough, irregular, calcified shells, where one shell cups the other. Mussels are outfitted with a mirror-image pair of smoother shells.
Marine oysters have elevated status in culinary circles, perhaps because their consumption is thought to boost libido. Consider that Casanova reportedly ate 50 oysters for breakfast each day. Reaching back to Greek myth, the oyster shell represented Aphrodite, the Goddess of sexual love and beauty. The Romans further believed that oysters possessed mystical powers capable of awakening dormant desires.
The not so revered Pacific coast mussel may find its way into a pasta dish or seafood bouillabaisse, but in my angling world they mostly serve as bait for surfperch and greenling.
Now, for what the famed radio announcer, Paul Harvey, used to call “the rest of the story.” A less known fact is that Native Americans from the Pacific Northwest harvested “river oysters” or xstu’ for more than 10,000 years.
In his award-winning book, When the River Ran Wild, George Aguilar, Sr, a Wasco elder, noted that river oysters grew in masses “usually in deep eddies of the Deschutes River.” Aguilar further wrote how this once common shell food was harvested across from the South Junction in the 1930s.
River oysters, i.e., freshwater mussels, once rounded out the fish part of the three-part subsistence lifestyle of mid-Columbia Sahaptin-speaking Indian tribes. The other two parts being roots and game. Early ethnographic surveys reported mussels were mainly collected from late summer through early spring. Villages located near mussel beds led to opportunity for harvest when other food resources were not available. Hence the terms “famine” or “starvation” food.
John Alan Ross writes in his seminal book, The Spokan Indians, how mussels were gathered in cedar or willow baskets of open construction that allowed water to drain quickly. Once shucked, they were baked, boiled, or steamed for consumption. Where plentiful, mussels were strung on twisted hemp line and dried in the sun or smoke-dried over low burning embers for later use in soups and stews. Some were eaten with pit-cooked tree moss.
Mussel shells served as spoons and serving dishes. Shell necklaces were used for decoration and possibly as a media of exchange in Columbia River trade networks. Empty shells were deposited in “middens” away from and downwind of riverine villages to reduce offensive odor and the attraction of insects and foraging animals. Many of these shell deposition sites have since been flooded with backwater of mainstem dams.
Of the 297 known species of native freshwater mussels in the United States – the majority which occur in east of the Continental Divide–only 70 species are considered to be stable. A century of overharvest for pearls, and for button and cultured pearl production, has led to a virtual collapse of a once-thriving industry in waters in the Mississippi River Basin.
Three common genera occur in the Pacific Northwest, including the western pearlshell, the western ridged mussel, and floaters. Each of them has declined in range and abundance in over the past century.
The long-lived pearlshell (up to 100-years or more) grows in dense colonies. Historical evidence suggests that pearlshells were common throughout the Columbia River system. No so anymore in impounded waters of the mid-Columbia, although a recent survey by Walla Walla University researchers identified a “robust” population of pearlshells in a riverine section of the Clearwater River.
Less is known about western ridged mussels. This elusive mollusk has a thicker shell than floaters and lacks the well-developed “pseudoocardinal teeth” of the pearlshell. Hopefully, ongoing surveys by regional tribal scientists and the U.S. Fish and Wildlife Service– two resource management groups with primary vested interest in protecting and restoring imperiled freshwater mussel populations– will yield more information about their status.
The common name “floater” refers to all North American species of thin-shelled Anodonta. Floaters use their pseudopodia or soft, muscular “foot” to move along the bottom of the river. During the 1992 test drawdown of Lower Granite and Little Goose Dams, floaters left shallow furrows in soft sediment when they attempted to follow receding water levels to safer depth. Some burrowed into the sediment and became desiccated. Also unlucky were mussels left exposed and vulnerable to marauding birds and mammals when reservoir levels were dramatically reduced for several months during repairs made to Wanapum Dam in 2014.
Mussels depend on a host fish, such as juvenile salmon, to serve to complete their life cycle and expand their range. Tiny bivalved larvae called glochidia are expelled by the female to attach to the gills or fins of a fish where they undergo metamorphosis into the adult mussel form. Following metamorphosis, mussels detach from their host fish and settle down to partially burrow in the river bottom.
While the life of a freshwater mussel may seem simple, there are threats to their existence. The introduced Asian clam may compete for food or space. The occurrence of invasive zebra and quagga mussels is also of concern. Declining numbers of salmon and steelhead as host fish further limits mussel distribution and abundance.
Why should we care about freshwater mussels? For one, they recycle nutrients. By filtering large volumes of water, they also serve as biomonitors of water quality. Their spent shells stabilize sediments and provide habitat for aquatic insects and juvenile fishes. Mussels can be important food items for river mammals such as mink, otter, muskrat and raccoon. Sturgeons also feed on mussels.
The cultural significance of mussels is deeply rooted in tribal lore. A brief passage in the book, Nez Perce Coyote Tales: The Myth Cycle, describes how Mussel-Shell Woman tempts the trickster Coyote to join her. “You there. Come this way and sleep with me,” she says. Attracted by her seductive voice, Coyote is taken in and squeezed to death by Mussel-Shell. The connection to Casanova is unmistakable.
One goal of area tribes is to restore depleted mussel populations to a level that allows for limited traditional harvest. Their task is daunting, given threats from invasive species, aquatic habitat loss, and competing water-use issues. Regardless of whether you call them river oysters or mussels, these fascinating creatures deserve protection for future generations to appreciate and for their role in maintaining the balance of nature.