Friday, September 18, 2020
Sept. 18, 2020

Linkedin Pinterest

Protecting freshwater mussels a growing concern

Scientific community’s expanding knowledge calls into question their future

By , Columbian staff writer
Published:
4 Photos
In this 2009 photo, Jeff Jolley, then with the U.S. Fish and Wildlife Service, holds a Western pearlshell mussel found in Salmon Creek.
In this 2009 photo, Jeff Jolley, then with the U.S. Fish and Wildlife Service, holds a Western pearlshell mussel found in Salmon Creek. (Al Smith) Photo Gallery

Odds are good you didn’t even known freshwater mussels are native to the rivers and streams of the Pacific Northwest — including those that run right through the heart of Clark County.

That’s not at all unusual. Even many researchers don’t, say members of the small but tight-knit group of scientists and retired wildlife agency officials who study them. But as the scientific community’s scant body of regional freshwater mussel knowledge grows, so do their concerns about the animals’ future.

Scientists don’t know much about the handful of native freshwater mussel varieties that live in the Western United States. They’re believed to have been abundant throughout the Northwest and beyond before modern humans began dramatically altering the landscape. Now researchers believe their populations and distributions are shrinking; and to boot, they don’t appear to be as physically robust as their forbearers.

“Those of us who have watched environmental degradation — for me, it’s been 40 years — you can’t help thinking they’re declining. But that’s not a quantifiable assessment,” said Al Smith, a retired fisheries biologist.

Smith has spend close to the last 20 years since he retired studying and observing freshwater mussels from Washington to California. He’s credited by many in the field for amassing a large volume of observation records.

Home to at least 300 different varieties, North America claims the broadest array of freshwater mussels of any continent in the world. But the situation is grim. The Nature Conservancy reports that about 70 percent of mussels in North America are extinct or endangered.

The mussel that the public is likely most familiar with is the zebra mussel, an invasive species native to central Europe. Although those creatures usually grow to about a half-inch, or less, they reproduce voraciously. A single mussel bed can contain tens of thousands of individuals within 1 square yard. When a colony establishes itself, they can cause serious damage to boats, city water systems, power plants and more. Also voracious eaters, they can significantly reduce food supplies for native creatures.

The majority of North America’s native freshwater mussel species are east of the Mississippi River. There are perhaps seven varieties that are native to the Pacific Northwest. Mussels have been spotted in Salmon Creek, Burnt Bridge Creek, Vancouver Lake, the Columbia, Washougal and Lewis Rivers, just to name a few. There are possibly more out there, but scientists aren’t studying them.

Smith and other researchers say mussels in the Eastern United States are better understood because they’ve been studied for decades. Many Eastern varieties are listed as endangered species –which brings crucial funding to better understand and restore imperiled animals.

He worries that this region’s mussels are in a kind of Catch-22 situation: He thinks they’re probably in decline, but without the money to create true before-and-after population comparison surveys, scientists can’t determine their conservation status; but without knowing their conservation status scientists can’t get the funding to study them and possibly intervene if necessary.

“I do presence/absence surveys,” he said. “I go out and find where they were and see if they’re still there. It’s a quantum leap between what I do and what needs to be done.”

While a key species for many freshwater habitats, freshwater mussels are unostentatious and haven’t captured the public’s imagination or financial resources the way cuter or more charismatic threatened species have. They lack the playful charm and cuddly appeal of sea otters; the power and grace of orcas; and the cultural, nutritional and economic value of salmon.

“They’re another species that’s in the environment that people have neglected because they’re not flashy and people don’t understand them — and they honestly look like a rock,” said Emilie Blevins, a conservation biologist with the Xerces Society. “They fall into this gap of not being an economic resource or being really big or exciting, but I’d argue their water quality benefits are undervalued.”

But the humble mussel might be inextricably linked to salmon restoration. Indeed, during a survey study in Burnt Bridge Creek at Leverich Park, Blevins stepped into the creek and spotted a salmon carcass and a western pearlshell mussel nearby.

Western pearlshells depend on salmon to complete part of their life cycles. Tiny mussel larvae attach themselves to the gills or fins of out-migrating salmon or steelhead and live off of them until the fish return to the river. When they do, the mussels bust out and bury themselves in the streambed until they’re large enough to not be eaten by predators.

“The other mussel species are much less discriminatory but we don’t know what their preferences are,” Smith said. “In the Northwest, there isn’t money to do that kind of work.”

‘Liver of the river’

Once they’re in the water, the animals play a big role in a waterway’s ecology.

Mussel enthusiasts use several metaphors and similes to describe the animals’ role in nature:

• The liver of the river — for their ability to filter out harmful containments and process nutrients so that other organisms might consume them.

• An underwater aspen grove — for the way a large colony lives its entire adult life in one place, with individuals potentially reaching 100 years or more in age.

• A freshwater coral reef — because so many other species live around and benefit from the habitat they create.

Freshwater mussels can eat E. coli bacteria and filter pharmaceuticals, heavy metals and other toxins out of the water. They reduce water turbidity and hold river bottoms in place, which allows plants to grow and gives habitat to other creatures and better spawning habitat for fish. Like their marine cousins, freshwater mussels are filter feeders. What they eat turns to waste, which helps vegetation grow; what they don’t eat they spit into small pellet-like clumps that invertebrates eat, which, in turn, are eaten by baby salmon and other fish.

But like any creature, there’s only so much pollution or other stressors they can handle.

“Mussels need more attention than they’re given. We consider them ecosystem engineers. Like the beaver, they change their habitat to suit their own needs … (which) makes it better for them and other organisms. Mussels do the same thing, just on a different scale,” said Alexa Maine, an aquatic propagation laboratory manager and fisheries biologist.

Maine is blunter about society’s conservation priorities than Blevins. “If they’re not good to eat then people don’t care, and, in general, freshwater mussels are better in the river than in your stomach,” she said.

Maine works for the Confederated Tribes of the Umatilla Indian Reservation in Oregon, the only organization in the Western United States — public or private — that propagates mussels for population restoration.

The tribes are following a “first foods management plan,” meaning they’ve identified food resources like salmon, lamprey or mussels that were once used for cultural and subsistence purposes.

Archeological digs around ancient Native American sites have uncovered sizable deposits of ancient shells.

Smith described them as a meal of last resort for ancient people.

“They taste like mud. But they’re always there and were almost certainly in every waterway.”

But now, here and across the country, mussels face grave circumstances.

“We are finding and documenting examples of large “enigmatic die-offs,” meaning that all the mussels in an area are dying suddenly and there is no known cause,” Blevvins wrote in an email. “We also see mussel beds beginning to disappear because they are not reproducing.”

All that is not to say the mussels are ignored. Slowly but surely, more organizations are recognizing their importance. A few years ago, Washington prohibited harvesting them. The Washington Department of Fish and Wildlife has a portal where people can report mussel sightings, which are then added to a database. In Oregon, the Willamette Riverkeeper is also studying them. The Xerces Society has also published a best practices guide for protecting native mussels during aquatic restoration projects.

Still, more awareness is needed if they’re going to be protected — especially when climate change is predicted to raise river and stream water temperatures.

“You can’t save something you don’t know about,” Maine said.

Loading...