( The rusty crayfish - a voracious bully...)Study shows hope for ridding lakes of clawed invader

Since its introduction to Wisconsin waters sometime in the 1950s, the crayfish has spread to thousands of lakes and streams, clear cutting the underwater forests that are critical fish habitat, evicting the native crayfish from one body of water after another and scooping up fish eggs like so much caviar.

But the clawed invader, the early results of a long-term University of Wisconsin-Madison study suggest, may be vulnerable to a "double whammy" of intensive trapping and predator fish manipulation to the point where it may actually be possible to rid lakes of an animal that has vexed scientists, anglers and conservation agencies alike for decades.

"They pretty much wipe out all of the rooted aquatic plants, they eat fish eggs, they either eat or compete with native invertebrates and, in general, raise havoc with the near-shore community of a lake," says Stephen Carpenter, a UW-Madison professor of limnology and zoology involved in the study on Sparkling Lake in Vilas County, Wis.

Supported by the National Science Foundation (NSF), the long-term study of the feasibility of evicting the rusty from the 110-acre lake is now in its sixth year. It holds the promise of a rare victory in the war against introduced invasive species.

Since 2001, the UW-Madison researchers, aided by a small army of undergraduate students and the Wisconsin Department of Natural Resources (DNR), has succeeded in significantly reducing the population of rusty crayfish in Sparkling Lake through a program of intensive trapping and manipulating fishing regulations to favor the smallmouth and rock bass that dine on juvenile crayfish. The two-pronged attack, says Carpenter, has yielded very promising results.

"It seems to be working. The aquatic plants are back. That's good because that's fish habitat, an
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Source:University of Wisconsin-Madison