UW professor leading effort to eliminate invasive crayfish in Pine Lake
March 6, 2013
By Ari Cetron
Back in the late ‘90s, a teacher made a boo-boo. After completing a lesson on crayfish, the teacher dumped them into Pine Lake. Unfortunately, these weren’t ordinary crayfish. Well, not ordinary for this part of the country.
And so, the red swamp crayfish started taking over the crayfish niche in the lake, according to Julian Olden, a freshwater ecologist with the University of Washington. Now Olden, with the help of volunteers from around the lake, aims to stop them.
“Preventing its future spread is a real possibility,” he said.
The crayfish native to the lake, the signal crayfish, typically grow to about 3 inches long, though some can reach up to 7 inches. It looks kind of like a cross between a small lobster, a big bug and a tiny, tiny sea monster. According to Olden, they play a central role in the food web, eating animals below them, such as snails, and animals above them, such as fish eggs.
“All crayfish play that role, but some are more aggressive than others,” Olden said.
The red swamp crayfish fit into that “more aggressive” category. Bigger and burlier than their native cousins, the red swamp crayfish are a bit too good at what they do, at least in this area. So their presence could hurt the overall lake health if they eat too many of the other animals, particularly if they eat the eggs of commercially or recreationally important fish, Olden said.
Pine Lake, Olden said, is a good place to try and stop them. It was the first place in the state where officials first noticed the red swamp crayfish, in 2000. Since then, they’ve found them in nine other lakes around the state, including Beaver Lake.
But in Pine Lake, the problem is more acute. Olden said recent estimates are that the invasive crayfish outnumber the natives by a four-to-one ratio. Though that number has varied over the years, it’s been trending in favor of the invaders.
Olden said he hopes that by stopping the crayfish in Pine Lake, they can not only help the lake, but also stop the spread of the little crustaceans. Along the way, he hopes to teach lake residents a bit about how they can keep a lake healthy.
“While it’s a restoration effort, it’s also a big education effort,” Olden said.
One person who’s signed on is Kate Bradley. She knows the lake well, having lived on it for 15 years. She’s also spent time as a volunteer collecting water quality samples.
Bradley has been sharing the temperature data she collected with Olden and has helped organize the effort to rally lake residents to catch the invaders.
“I’m just interested in Pine Lake,” Bradley said.
She, along with some neighbors, will be setting traps off their private docks.
When they check the traps, hopefully at least twice a week from July to September, they are supposed to remove the red swamp crayfish and return the native crayfish.
Once she’s got some crayfish, Bradley said she will measure it and check its sex. Then she has two choices. She can either freeze them so Olden and his team can study them, or she can cook and eat them.
Bradley said she hopes that families around the lake will join in the effort, especially families with children, who might enjoy studying the creepy-crawly critters.
“I think it’s something that will really interest young people,” she said.
The effort will be undertaken entirely from private docks, Olden noted.
He expects it could take a few years before they can tell if the project is a success.
The first meetings about the effort haven’t taken place yet, so its difficult to estimate how many of the docks will have traps dangling from them. While these sorts of projects are usually led through a state agency, this time it will be done through citizen volunteers who live on the lake.
Public fishing and swimming from the dock at Pine Lake Park will not be impacted, so there shouldn’t be a chance anglers will get their line caught or young swimmers will stumble into a trap in the warm summer months.
“We are avoiding a free-for-all of everyone going out there and trapping like mad,” he said.
Winter side effects
Red swamp crayfish are native to Louisiana and other southern states, said Julian Olden, a freshwater ecologist with the University of Washington. As a result, they don’t typically like cold weather.
“The running prediction is that mild winters might promote growth,” Olden said.
He noted that the warmer water temperatures can help the red swamp crayfish both survive more easily and encourage reproduction. This year’s mild winter, then, might lead to a bump in the non-native crayfish population in the future.