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Friday, July 28, 2006 - Page updated at 07:39 AM


Louisiana red swamp crayfish changes life in a Sammamish lake

Seattle Times Eastside bureau

The problem of the invasive crayfish in Sammamish's Pine Lake probably started innocently enough.

Perhaps a fisherman tossed his live bait in the water years ago. Or a child decided to set her aquarium creatures free.

However the Louisiana red swamp crayfish ended up in the lake, Karl Mueller is certain of one thing: They are overrunning the native signal crayfish at a fast clip.

And that shift is changing the entire freshwater ecosystem of the lake, he said.

"They've really done a number on it," Mueller said.

Mueller, a former biologist with the state Department of Fish and Wildlife, has been camped out at Pine Lake for several weeks observing the two species of crayfish duke it out for survival.

How to prevent the introduction of non-native species

If fishing with live bait, do not empty the contents in the water. Dispose in the garbage.

Find fish-rescue groups on the Internet that take unwanted aquarium animals. Or kill them humanely by freezing them in a plastic bag. Dispose of in the garbage.

Do not release live aquatic wildlife found at seafood markets or classroom biology labs into the water.

Remove any visible vegetation from boats after use.

Source: Washington Department of Fish and Wildlife

All his data point to the fact that the invasive Louisiana red swamp crayfish — which hail from the South and northeast Mexico — are outnumbering the native signal crayfish by a ratio of 3-1.

What this means is that the numbers of native crayfish could dramatically decline and might disappear, he said.

"In a larger sense, it's the homogenization of wildlife," Mueller said. "You could compare it to what's happening with retail in America. The same stores are everywhere now. In nature, you're not supposed to have that."

No agency tracks how many invasive species of crayfish inhabit lakes. But in King County, the Louisiana red swamp crayfish also has been recorded in Lake Washington and Steel Lake. Although considered a delicacy, red swamp crayfish are a prohibited species in Washington, meaning they must be killed before being transported.

Mueller, 44, discovered the red swamp species in Pine Lake six years ago when he was a state biologist. It was the first time the non-native species had been officially reported in Washington.

He later left the job to go back to school but could not get the critters out of his mind. What would happen if the red swamp crayfish were left to flourish? How would this affect the signal crayfish that had inhabited the lake for generations?

Now a graduate student at Western Washington University, Mueller is observing the ongoing turf battles between the signal and red swamp crayfish this summer as part of his master's thesis. He charts how the crayfish — burrowing creatures by nature — compete with each other for shelter.

Mueller has collected between 130 and 140 red swamp and signal crayfish from the lake and divided them into separate wire-mesh enclosures. The enclosures contain roughened pipe that the crayfish use as shelter.

On a warm morning last week, Mueller donned a snorkel mask and fins as he dunked in and out of the water, depositing the crayfish. He then placed the enclosures back into the water. Later, taking notes with a pencil on waterproof paper, he spent two to three hours kneeling in a dry suit at the bottom of Pine Lake watching the crayfish guard their shelter.

There's no doubt the red swamp crayfish are more aggressive, Mueller said. He's seen them kill and eat the signal but has never watched it happen the other way around. He has been bitten by red swamp crayfish more times than he can count, he said. Once, a red swamp latched onto a nerve on his finger with its pincers and wouldn't let go.

"They are really predator-savvy," he said.

The red swamp crayfish also reproduce more rapidly, producing double the eggs the signal produces.

"They are just plowing through food," Mueller said.

The rampant feeding and burrowing create a domino effect in the lake. The activity releases nutrients such as phosphorus into the water, which leads to more algae bloom, which could suffocate the lake.

"Up, down, across, it's all affected. It's all connected," he said.

Pam Meacham, acting aquatic invasive species coordinator for the state Department of Fish and Wildlife, said what's happening at Pine Lake epitomizes how one small action can wreak environmental havoc.

"People have this bad habit where they get tired of their aquarium or goldfish bowl and dump them in the nearest pond or lake," Meacham said.

"But that 10-cent goldfish can get to be about 2 feet. This agency has literally removed truckloads of goldfish out of Newman Lake in Spokane."

Fisheries biologists with the U.S. Fish and Wildlife Service said Mueller's research will be valuable if the signal crayfish ever are designated endangered species.

As far as Mueller can tell, the red swamp crayfish are here to stay.

So now it becomes a matter of making sure the problem doesn't get worse, he said, by keeping the invasive crayfish out of other bodies of water.

"The ticket is trying to prevent further introductions," he said.

Sonia Krishnan: 206-515-5546 or

Copyright © 2006 The Seattle Times Company




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