Travis Williams of Willamette Riverkeeper searches for mussels near Skinner ButtePhoto by Camilla Mortensen

Mussel Mania

The plight of Oregon’s freshwater mussels

Standing chest deep in the chilly waters of the Willamette River, Travis Williams of Willamette Riverkeeper scans the water for mussels. The flow is high on a cold October day, and as I gingerly climb down the muddy bank and into the waters beside him, I too look for the dark shells Williams tells me are there, beneath the surface.

Thinking back to various floats I’ve done on the Willamette, I know I’ve seen mussel shells. I just never thought about them. On some level, I assumed that the bivalve remnants had somehow crept into the waters from the Pacific Ocean.

And that’s the thing with freshwater mussels. They tend to go unnoticed, unregarded and underappreciated.

We are next to Skinner Butte, the only pair of people in dry suits planning to plunge into the water, at a spot where Williams says he’s seen a bed of mussels in the past. It’s a good spot for them, he tells me — the flows aren’t too fast here and the riverbed is right for them.

Unfortunately, the water is too high and murky today to see any shells, and I turn down Williams’ offer to follow his example and plunge my face into the cold water and snorkel around.

I admit that I’m reluctant not only because it’s cold, but also because I worry about the Willamette being less than clean as it flows through town. I know I’m not alone in that fear, and that is one reason we need to learn to love freshwater mussels: They clean the river.

Before we part, Williams hands me a slim booklet, a field guide called Freshwater Mussels of the Pacific Northwest, put out by U.S. Fish and Wildlife Service and the Xerces Society for Invertebrate Conservation, among others. As I read it later, in the warmth of my office, I note that the word “unknown” comes up again and again in reference to which fish host the mussels in their larval stage, historical data and the long-term effects of the loss of native fish.

Despite being small, simple creatures, there is much we don’t know about the freshwater mussels of the West.

Mussels face the same challenges that salmon and other more charismatic species face, such as climate change, invasive species and dams. At the same time mussels are a key element in river health. Scientists and river advocates have been delving into mussels, where they are, how they survive and how to bring them back.

The Confederated Tribes of the Umatilla have taken that one step further as they look at mussels’ key role in the ecosystem as a tribal “First Food.”

Flexing the Willamette’s Mussels

Williams really began thinking about mussels in 2002 after the Willamette Riverkeeper group he heads up began to acquire Norwood Island, at the confluence of the Long Tom River and the Willamette, north of Corvallis. The $70,000 purchase that began in 2014 will be completed this year. Williams discovered a massive bed of mussels in a river channel along the island. “I looked down,” he says, “and the entire channel was littered with mussels. It blew my mind.”

This past summer Williams snorkeled 120 miles of the river, spotting other mussel beds along the way, including the one we tried to look at in Eugene.

Some of the Norwood mussels were quite large. As it turns out, freshwater mussels can be very long-lived. One species native to Oregon and the primary one found in the channel, the Western pearlshell (Margaritifera falcata) can live more than 100 years, making it one of the longest-lived animals.

Oregon is also home to the Western ridged mussel (Gonidea angulata), which lives 20 to 30 years, and the shorter-lived Oregon floater (Anodonta oregonensis) as well as other floater species. Floaters tend to live 10 to 15 years.

All of these are among the eight species found in the West. Contrast this to the eastern portion of the U.S. where 270 mussel species are found.

Holding the shell of a Western pearlshell in his hand, Williams points to the growth rings on the ancient mussel that show its age, in a way similar to tree rings, if one were to cut into the shell and analyze it. In Oregon, freshwater mussels can’t legally be plucked from their beds, and Riverkeeper had “scientific taking permits” from the Oregon Department of Fish and Wildlife for the study the group conducted this past summer.

Williams says when it comes to what’s important about mussels, it’s first of all “cool that these animals exist,” and “it is about instant respect just given their potential lifespans.” Also, he points out, mussels must interface with all of humanity’s collective actions, like pollution, to stay alive.

Celeste Mazzacano is an entomologist whose invertebrate studies led her to a fascination with mussels. She says the bed along Norwood Island is notable because it has a sandy bottom but the Western pearlshell mussels that dominate it tend to like it gravelly, and she’d never seen an aggregation of mussels that big.

“It was a real wow just to see that many of our native mussels in one place,” she says.

Mazzacano and her volunteers found lots of live mussels there, she said, but also lots of shells from dead mussels. “We know there’s a lot of mussels here,” she says, “but not much about them.”

Were they only Western pearlshells? Were there any young mussels?

As it turns out, there were really no young mussels, and there were some floaters in the channel. In a study published this fall on the Norwood bed that Mazzacano did for Willamette Riverkeeper, she noted that 90 percent of the 40,000 or so mussels in the channel were older, larger mussels, with only a few younger mussels and no juveniles.

“Some time in the somewhat recent past conditions were good for mussels, so what’s up here?” she asks.

Mazzacano says freshwater mussels in the Willamette, which she calls a “highly impacted river that gets a lot of abuse,” haven’t really been studied systematically. And people who have lived in the area a long time will say, “I remember when there were a lot more mussels in here. When I was a kid, they were all over the place.”

That statement alone says something about the importance of mussels, because mussels aren’t really something that stands out for many people, even people who think of themselves as river-lovers.

“They are not the sexiest animal that people take notice of,” Mazzacano tells me. “But they really are engaging. It’s like a treasure hunt; they’re kind of cryptic.”

She says she’s picked up a lot of rocks, thinking she was grabbing a mussel. When she finds one, “It’s a feeling of discovery.”


Volunteers assess mussel populations in the Willamette River

Photos courtesy Willamette Riverkeeper

The Liver of the River

Emilie Blevins is an endangered species conservation biologist with the Xerces Society. Like Mazzacano, she is fascinated by mussels. Butterflies and bumblebees are beautiful and attractive, she says, but mussels, burrowed into riverbeds, you don’t see unless you are specifically looking for them. “They are really interesting creatures with a really complex life cycle.”

And, she says, these seemingly dull little bivalves function as “the liver of the river.”

A mussel can remove E. coli, flame-retardants, pharmaceuticals, pesticides and heavy metals, she says. It cleans water, makes sunlight penetrate the water more deeply and helps other organisms like algae grow. Mussels benefit fish, birds and the river as a whole. She compares the mussels to a wastewater treatment plant.

If you were to look down — if only the water were clear enough — you would see a dark blackish-brownish shell and, beneath that, the mussel’s fleshy foot, holding it to its bed.

“That animal might have been there for 40 years,” Blevins says, “filtering water constantly as it’s flowing over it, giving it the oxygen that it needs, collecting food and filtering contaminants.”

And that fleshy foot anchoring the mussel down, keeping it largely in one spot for its lifetime, also helps stabilize the riverbed.

After the mussels clean the water and extract nutrients, what is essentially their poop falls to the river bottom and feeds tiny juvenile invertebrates that become aquatic insects and other creatures, which then feed fish and birds.

Healthy mussels are a sign of river health, she says, and when they start to decline, it’s time to become concerned.

Blevins points to another recent mussel study, this one done by Xerces and the Confederated Tribes of the Umatilla Indians, showing mussels have been lost from one out of five watersheds in which they once occurred in the West.

Xerces and the Umatilla created a database of mussel records from research and museum collections, historical publications, and public agency and personal records going as far back as 1834. The creation of the Western Freshwater Mussel Database took 10 years. While the work is impressive, the results are a little discouraging.

Using the criteria for the ICUN (International Union for Conservation of Nature) Red List of Threatened Species, the researchers found that the Western ridged mussel and winged floater are “vulnerable” — they have disappeared from more than 30 percent of their range, and the Western pearlshell is gone from more than 15 percent of its range and is considered “near threatened.”

The U.S. Geological Survey says more than 70 percent of the continent’s 302 species are extinct or imperiled. While they are ICUN listed, none of Oregon’s mussels are federally listed, meaning they don’t get special protections that could aid in their uncertain future. “In Oregon they are not protected other than the fact that you cannot harvest them, and you basically are not supposed to pick them up,” Williams says.


Unexplained die-offs like these are another reason for concern about freshwater mussels.

Photo courtesy Emilie Blevins, Xerces Society

Musseling Up

Mazzacano says Oregon’s freshwater mussels face a lot of challenges, and some of them — like climate change and habitat loss — they share with many other animal species.

In the case of climate change, rivers are heating up, making it more difficult for the mussels’ host fish. In terms of habitat loss, dams make it not only harder for the host fish, which often can’t get past dams despite fish ladders and even trucking, but also harder for mussels to have the right river flows, substrate (the gravel, rock or sand they dig into) and temperatures. Rivers below dams can be starved for sediment, she says.

And then there are those host fish. Freshwater mussels like the Western pearlshell have an “absolute dependence on host fish,” Mazzacano says. They are “salmon specialists” that need native salmonids to survive.

A mussel’s life cycle goes something like this: The male mussels release sperm into the water, and the females inhale it. Thus the name “bivalve” because mussels have one valve that takes things in and another that sends it out. Embryo mussels develop into larvae called “glochidia” and are released by the female mussels. (Interesting side note: It’s rare, but Western pearlshells can be hermaphrodites.)

Once released, the glochidia need the host fish. Blevins says some glochidia have hooks. Some don’t, but they find a way to grab onto a fish’s fins or gills, take a bite, hold on and encyst. The fish swims away and “the glochidia hang on for the ride,” she says.

While Western pearlshells need native fish like cutthroat trout, Chinook, Coho and sockeye salmon, floaters tend to be generalists when it comes to their fishy hosts. But all of Oregon’s freshwater mussel species need to be parasites on fish as part of their life cycles. Without the fish, the mussels cannot reproduce.

Musseling In

Oregon is home to invasive Asian clams — possibly brought here because people saw them as tastier than Oregon’s native mussels, Mazzacano says.

Or possibly, according to Alexa Main, they came to the Northwest via the Great Lakes, “as all the bad things seem to,” she says, only half in jest. Main is a mussel and Pacific lamprey biologist with the Confederated Tribes of the Umatilla Indian Reservation.

Asian clams not only can compete with native mussels for food, they may also consume larval or juvenile mussels.

Main points out that not only do dams limit the mussels’ access to native fish, but mussels are also up against nonnative fish. Nonnatives will eat the host fish, and native mussels are not interested in latching on to most nonnative fish — similar, Mazzacano, says to caterpillars that only like to munch on one type of plant.

And that’s not all that Oregon’s unobtrusive mussels are up against. There are also invasive mussels — zebra and quagga mussels, malignant little bivalves that have been invading lakes and rivers across the country. They have not made it to Oregon. Yet.

One economic assessment showed that a mussel invasion would damage hydropower, irrigation, fish hatcheries and municipal water facilities at a cost of $500 million annually to the Pacific Northwest.

“They don’t need a host fish; they shoot out the baby mussels,” Mazzacano says of the invasives’ reproductive technique.

And while Oregon’s native freshwater mussels take years to grow up and reproduce, zebra and quagga mussels mature quickly and could compete for mussel habitat.

But if Oregon’s mussels are in decline, you might think the invaders could fill in the niche that mussels have in filtering water. Unfortunately, zebra and quagga mussels reproduce so quickly the filter feeding they do “almost sterilizes the water,” Mazzacano says. Rather than benefit, they damage the ecosystems they invade.

Mussels and First Foods

Thanks to the Confederated Tribes of Umatilla Indian Reservation in northeast Oregon, mussels west of the Continental Divide are the subject of the region’s only effort to re-propagate freshwater mussels.

The Umatilla, however, came to the mussel quandary and restoration differently. According to tribal member Wenix Red Elk, the CTUIR mussel effort came about as a result of the tribe’s First Foods policy.

Red Elk explains, “When you lose a food source, you lose the food source but you are also losing the entire culture of that river area, that fish, that land” and the culture, the language and family stories that went with it. “It’s so much bigger than losing a species.”

First Foods, she says, are “natural, from that land, and have always been there, at least for us. For us, First Foods are the foods we were given by Creation.”

Tribal belief says the Creator asked the foods which of them would take care of the people, and salmon was the first to promise, then other fish and mussels lined up behind salmon. The First Food serving ritual in the longhouse follows that order. First Foods are water, salmon, roots, berries, deer and elk.

While a Eurocentric viewpoint might try to save the salmon, the First Foods-informed perspective means mussels, lamprey and other key elements in the ecosystem must be saved as well in order to save salmon.

The tribes have a reciprocal response to those foods, Red Elk says. “The foods give life to us, and in turn, we protect them.”

She says the tribes “have been doing this type of work from time immemorial,” and they gather what they need, whether it is salmon, willows or wood for teepee poles, in such a way they come back more plentiful.

Elders tell stories of where mussels were and where they were eaten, and that information — the knowledge of the people — is brought to the scientists. “That’s what’s so unique about us,” Red Elk says. “We put that oral history first.”

This approach brings attention to species and ecological processes that those outside the Umatilla reservation may not recognize or value. Traditional ecological and cultural knowledge is brought together with science.

“Our keystone river is the Umatilla River,” says Main of the CTUIR mussel project. “First Foods takes the entire river as whole, takes the pieces of what we want to see, and breaks it down into individual components. Not just a salmon run in 10 years, but everything that goes into a healthy ecosystem.”

Back in the 1960s and ’70s, Main says, Western pearlshells were made locally extinct in the Umatilla River. The Umatilla, Cayuse and Walla Walla Indians used pearlshells exclusively as a food source, and for jewelry and tools.

“It’s really telling to see we’ve completely extirpated that from an entire system,” she says.

Elizabeth Glidewell is the Freshwater Mussel Project lead for the CTUIR. She says the project started in 2003 and, while it has gathered vast amounts of historical data, she echoes the cry that there is still much to discover about mussels, from where they are and how many are left to their reproductive timing.

But, she says, the project is “close to being able to address the long-term goal of restoration.”

Working with mussels, Glidewell tells me, is a way of “cheering for the underdog.”

Knowing that the pearlshell uses salmonids, Glidewell says that scientists can take the mussel larvae and attach them to the fish, and give them time to metamorphose in a lab setting. They can then be collected and released into the river as juveniles or later on.

Aware of the argument that salmon raised on fish farms are genetically inferior, and even stupider, and thus less able to survive than wild salmon, I ask Glidewell if that is a concern for something as small and seemingly brainless as a mussel.

“We don’t think so,” she tells me. They are selecting for traits that will let the mussels survive in the river and with good genetics.

Main adds that the plan is to out-plant mussels into the Umatilla River in 2018 or, at the latest, 2019.

Back in Eugene, on the banks of the Willamette, Williams tells me that one thing those working on mussels do know is that overall, Western pearlshells are declining.

Maybe, just maybe, he says, if enough information about mussel distribution and abundance is collected, they could be petitioned for listing under the federal Endangered Species Act. “But right now,” he says, “I don’t know of anyone working on that.”

To find out more about Willamette Riverkeeper’s efforts to document mussels in the Willamette, go to To see Xerces Society’s mussel research, check out Find the CTUIR mussel project via

Comments are closed.