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Crayfish Turf Wars Of The Northwest

July 15, 2013 | KUOW
CONTRIBUTED BY:
Ashley Ahearn

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  • Red swamp crayfish aren't native to the Northwest but where they've been introduced, they're taking over. credit: Ashley Ahearn
  • The signal crayfish (foreground) has lived in waterbodies of the Northwest for 10,000 years but it doesn't breed as often or produce as much offspring as its invasive red competition. credit: Ashley Ahearn
  • Julian Olden, a freshwater ecologist with the University of Washington, has been studying the red crayfish takeover of Pine Lake near Seattle. credit: Ashley Ahearn
  • Olden has enlisted lakefront homeowners to document and remove red swamp crayfish by setting traps like this one off their docks. credit: Ashley Ahearn
  • Solana Henderson, a Pine Lake resident and expert crayfish trapper, handles her latest catch as mom Renee looks on. credit: Ashley Ahearn
Red swamp crayfish aren't native to the Northwest but where they've been introduced, they're taking over. | credit: Ashley Ahearn | rollover image for more

PINE LAKE, Wash. — Gumbo and jambalaya may not be at the top of Northwest menus. But if the invasive red swamp crayfish has its way, that could change.

The Red Swamp Crayfish – also known as “crawfish” or “crawdad” – is native to the Southeastern U.S. and the Gulf Coast. But over the past decade this crimson-clawed invasive has moved in on some Northwestern lakes and rivers, and it could be impacting native species of trout and bass.

Ground zero of the invasion? Pine Lake. It’s a small body of water 40-feet deep, about 20 miles east of Seattle. The shores are lined with nice homes. Yellow labs patrol well-maintained yards and docks. Bass and trout fishermen share the water with laughing kids on paddleboards.

But the ecosystem balance of this lake is shifting, says Julian Olden, a freshwater ecologist with the School of Aquatic and Fishery Sciences at the University of Washington. Invasive red swamp crayfish now outnumbers the hometown species, known as signal crayfish.

“It started off being a 1-to-1 ratio 13 years ago,” Olden says, “and now we’re seeing anywhere between 5-to-10 times the number of red swamp to every one native signal crayfish.”

To keep tabs on how the population dynamics are changing, Olden has been setting traps regularly around the lake and tallying up the numbers of red swamp vs. signal crayfish he catches.

From his seat at the back of the canoe, Olden pulls up a trap and gingerly picks out a flailing red crustacean.


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Pine Lake was the first place in Washington where the red swamp crayfish were documented. They’ve since shown up in nine other lakes in Washington. Wildlife managers have also reported them in a few places in Idaho and the Willamette River in Oregon.

“They pinch you and they hang on for a little while,” he says, before putting the crayfish down in the bottom of the boat. He talks on as the 4-inch mini-lobster waves its claws and scuttles around, dangerously close to his bare toes.

This wasn’t natural colonization, he says. In at least one instance these crayfish were intentionally released after being used for research or as classroom pets, and they could be changing the native ecosystem.

“They will eat tadpoles, fish eggs, so they have direct effects through consumption and indirect effects because they’ll eat a lot of these aquatic plants that provide cover for young fish,” he says.

Olden pulls up another trap and out plops a member of the home town team — a signal crayfish. They’re called signal crayfish because of the bright white stripes on the inside of their claws. Underwater they flash like signals. Their backs are a deep ocean blue.

“Take a look at the blue color on that,” Olden says, his native-species loyalty clearly showing in his voice. “And then you flip them over and they’ll have this blue tinge and a red on the underside of their claws. Just gorgeous color.”

Signal crayfish have lived in this region for the past 10,000 years or so. But it only took a handful of years for the red swamp crayfish to take over.

Signal crayfish don’t breed as often as their crimson competition, and when they do, they don’t produce as many offspring. They also prefer cooler temperatures so in the future, things may not look good for them.

For now anyway, they’re getting some help in the fight against their non-native competition.

Olden finishes checking this round of traps and points the bow towards the far corner of the lake. The canoe moves quietly past dock after dock with signature red and white buoys marking traps the waterfront homeowners have put out to capture the invasive crayfish. Olden has involved the community in his research and management efforts.

The canoe arrives at the Henderson family’s dock as Renee Henderson and her daughter, Solana, come down to say hello. The Hendersons are among the 40 or so homeowners on Pine Lake who are working with Julian Olden to trap the invasive crayfish.

At 8 years old, Solana is one of the lead trappers. She crouches down on the dock and hugs her knees as she talks.

“I like picking them up because you can feel the scales kind of like, it’s rough and stuff and I like feeling that part,” she says. Then the girl describes “whopper” of a 69-millimeter crayfish she caught the other day.

Renee Henderson says the invasive crayfish are actually pretty tasty.

“We’ve done a lot of Googling recipes for crayfish pie, crayfish boil,” she says, smiling at her daughter. “It’s been good for her just learning about the environment and how to protect it. She’s obviously into science.”

All the participants in Olden’s study keep data sheets tallying up how many crayfish they catch and what the break down is between red swamp crayfish and the native signal crayfish.

So far Pine Lake residents have trapped and removed around 500 red swamp crayfish this year. Olden says some years they’ll catch upwards of 800 invasive crayfish.

“On days like this with all these people with traps in the water you’re pretty inspired that we might have a chance,” he says. “Eradicating them is not the goal here, that’s pretty much impossible. But controlling them to low enough level where their impacts are minimized, that’s what we have our eye on and hope will happen over the next couple years.”

Olden hopes that this model of community engagement can be replicated in other waters where the invasive red swamp crayfish has staked its claim.

© 2013 KUOW
Red Swamp Crayfish freshwater ecology Signal crayfish Pine Lake invasive species
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