Invader After Louisiana's red swamp crayfish show their pincers in Germantown, the DNR uses a new rule to fight back

Sep. 5, 2009
The Milwaukee Journal Sentinel

Germantown -- It's not good news, but the timing couldn't be better.

State authorities have discovered in a local pond a destructive Gulf Coast crayfish that's caused environmental damage in other states where it's showed up.

The Department of Natural Resources said personnel have caught hundreds of Louisiana red swamp crayfish over the last few days in a 6-acre pond of a subdivision south of Mequon Road, between Division and Pilgrim roads.

The crayfish are larger than native crayfish, and those that have been caught by the DNR have been up to 8 inches long. They've been plucked from the water and have been found crawling over neighbors' lawns.

Residents say the red crustaceans began showing up in June.

Now the DNR is trying to determine whether they have moved through storm water drains into other ponds in the area that eventually lead to the Menomonee River.

"We wish we would have known about them earlier," said Randy Schumacher, fisheries supervisor in southeastern Wisconsin, as he opened a cooler containing about 50 crayfish caught Friday.

The good news, however, is that with new regulations that went into effect just days ago, officials say they now have more enforcement powers to control new invasive threats such as the Louisiana red swamp crayfish.

Feisty and fast

Invasive species are a growing environmental threat in Wisconsin. They range from last year's discovery of the tree-killing emerald ash borer to European mussels that are wreaking havoc on the water chemistry of Lake Michigan.

The latest is a feisty, hole-burrowing crayfish that brandishes its large claws in defense, or shoots through the water with the speed of a fish.

Gary Peterson, a resident of Esquire Estates subdivision for 10 years, assumes that someone dumped the crayfish in water behind his backyard.

"That's not something you should do," Peterson said.

The Louisiana red swamp crayfish is popular in Gulf Coast cuisine. Its native habitat is in fresh water along the Gulf Coast from northern Mexico to the Florida panhandle and inland to southern Illinois.

However, it's considered a threat in Wisconsin and other areas outside its native range because of its aggressive nature and big appetite.

In Alaska, it's been known to eat salmon eggs. In Washington state, it has a penchant for digging on stream banks, causing erosion and algae blooms. And in Maryland, the interloper has harmed native populations of crayfish.

In Wisconsin, the new crayfish could out-muscle smaller native crayfish, according to Heidi Bunk, a DNR biologist.

By eating native plants and aquatic habitat, it also has the potential of upending local ecosystems.

And, Bunk said, it is capable of crawling several miles in places where there is a lot of water.

The crustacean's mobility worries the DNR because of its proximity to the Menomonee River. On Friday, crews rigged wire mesh on storm water drains and at an outflow away from the pond.

The DNR is using nets and traps to catch crayfish, which will be euthanized. The agency is also mulling other methods of lethal control, such as a chemical that could kill the crayfish but not harm other wildlife.

The DNR has also received help from neighbors. One property owner reported that she has run over crayfish with her lawnmower.

And on Friday afternoon, Nick Holcomb, 13, and his friend Adam Fretchel, 14, were using nets and a slingshot to catch and kill the crayfish. Holcomb said the pair have caught about 20 and cooked and eaten about five of them.

"They taste like shrimp almost," Holcomb said.

State officials don't know how the new crayfish got here. But some possibilities are that they were dumped from an aquarium, they were leftovers from a crayfish boil or they were used as bait.

It would not be unlawful to buy the crayfish, but it is illegal to release them into a public waterway.

DNR assesses new threat

The DNR got its first call about the crayfish Aug. 25. The agency confirmed it wasn't a native species the next day with the help of experts at the Milwaukee Public Museum. It then began setting traps to determine the extent of the population.

In Wisconsin, the Louisiana red swamp crayfish is considered a pioneer invasive species under new regulations that give the DNR more power to identify, search for and, if necessary, eradicate plants, insects and wildlife that are not native.

In the case of new threats, the DNR is able to rely on stronger enforcement powers to control populations on private property, according to Tom Van Haren, a natural resources policy officer with the agency.

The new rule was developed with input from the Wisconsin Council on Invasive Species and more than 70 environmental and business organizations, local governments and university experts.

Bunk said she deals with an average of one new pioneer species in southern Wisconsin each year.

Last year, it was an aquatic plant known as yellow floating heart, which has been found on storm water ponds next to Delavan Lake in Walworth County. The plant's canopy shades out native plants.

How the DNR will handle the new crayfish is unclear until the agency learns the extent of the infestation, Bunk said.

The agency is looking for what's worked elsewhere, said Jeff Bode, section chief of lakes and wetlands for the DNR.

The DNR has contacted limnologists at the University of Wisconsin- Madison who have had success in a long-term experiment controlling rusty crayfish, another invasive, in Sparkling Lake in Vilas County.

In that experiment, scientists controlled populations by trapping and by planting rock and smallmouth bass to feed on the unwanted crayfish.


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