Fighting (And Cooking) Invasive Crayfish In Northwest Waters

Jul 15, 2013

Gumbo and Jambalaya may not be at the top of traditional Northwest menus, but if the invasive red swamp crayfish has its way, that could change. The crayfish – also known as a crawfish or crawdad – is native to the Southeastern U.S. and the Gulf Coast.

But over the past decade this firey-clawed, and delicious, crustacean has moved in on Northwestern lakes. Ashley Ahearn reports for EarthFix.


Red swamp crayfish aren't native to the Northwest but where they've been introduced, they're taking over.
Credit Ashley Ahearn

  About 20 miles east of Seattle you’ll find Pine Lake. It’s a small body of water, only about 40 feet deep and lined with well-kept homes. Yellow labs patrol green lawns and sunny docks. Bass and trout fishermen share the water with laughing kids on paddleboards.

But beneath the surface… down in the depths of Pine Lake… no sharks here. But there’s a new creature on the block…with really big claws.

Olden: “This is called the red swamp crayfish.”

Julian Olden sits in a canoe on Pine Lake. He pulls a flailing red crustacean out of a trap and holds it gingerly as it waves its claws around.

Olden: "If they pinch you they hang on for a little while." Ahearn: “This spoken from experience?” Olden: “Yeah you have to convince them to let go but you can grab them right under their arms like that… “

Olden is a freshwater ecologist with the University of Washington. Over the past several years he’s been setting traps around this lake to monitor the advance of these aggressive intruders.

He puts the red crayfish down and it scuttles around the bottom of the canoe, dangerously close to his bare toes.

Olden: "It’s about 4-5 inches length total, so that's what you'd expect to see."

Olden says these intruders could be changing the native ecosystem. The red swamp crayfish eat tadpoles, bass and trout eggs. They also munch through the plants that line the bottoms of lakes like this one.

Olden: "And by basically being an underwater lawnmower they’re removing the home and cover for a lot of those native fish.”

You might call Pine Lake ground zero for the red swamp crayfish invasion. A biologist discovered them here in 2000. They've since shown up in 9 other lakes in Washington. Wildlife managers have also reported them in a few places in Idaho and the Willamette River.

Olden: "We're going to head over to this bay."

This wasn't natural colonization. In at least one instance these crayfish were intentionally released after being used for research or as classroom pets.

But on this lake anyway, the red swamp crayfish have been met with some local opposition. Olden pulls up another trap and out plops a member of the home town team – a signal crayfish.

Olden: “Take a look at the blue color on that. So these are olive brown on the top of them and then you flip them over and they’ll have this blue tinge and a red on the underside of their claws. Just a gorgeous color.”

Signal crayfish have lived in this region for the past 10,000 years or so. But Olden’s research has found that at Pine Lake anyway, they’ve been overtaken by the red swamp crayfish.

The blue-shelled locals 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.

Olden: “Hey Renee, how are you.”

Renee Henderson and her daughter Solana are among 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 to us.

Olden: "You were just telling me about the big whopper of a crawfish that you caught. How big was it?" Solana: "It was 69." Olden: "69mm long?" Ahearn: "Do you know how many you’ve caught?" Solana: "I pretty much don’t know." Ahearn: "If you were going to estimate – would you say 100 or 200 or 20?" Solana: "I would say 48."

Henderson: “We’ve done a lot of Googling recipes for crawfish pie, crawfish boil. 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 this year Pine Lake residents have trapped and removed around 500 red swamp crayfish. Olden says some years they’ll catch upwards of 800 of them.

Olden: "You know on days like this with all these people with traps in the water you’re pretty inspired that hey we might have a chance – not to remove them – eradicating them is pretty much impossible – but controlling them to low enough level where their impacts are minimized, that’s what we hope will happen over the next couple years."

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

Copyright 2013 Northwest Public Radio