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Content: Since leaving their native range in the Ohio River Basin (Ohio, Indiana, Kentucky, Tennessee), the rusty crayfish has been recorded in 20 other states, mostly to the north and east. The highest concentration of invasive rusties is in Wisconsin, where they have been recorded in 860 water bodies by the Wisconsin Department of Natural Resources. At the St. Croix National Scenic Riverway, their presence has been verified in the St. Croix River, although their populations appear to have remained largely south of where the Namekagon River meets the St. Croix. How do we stop them? It is unusually difficult to remove a population of rusty crayfish once it has become established. Chemicals are unusable because they affect native crayfish. There have, however, been scattered success stories where trapping and the encouragement of native predators (bass and sunfish) have been able to eradicate loosely-established infestations. Rusties can be trapped and boiled for food, as Wisconsin DNR law NR 40considers eating a legal form of disposal so long as the trapper has a fishing or scientific collector's license. Prevention, ultimately, is the best method of control. At the St. Croix National Scenic Riverway, the use of live crayfish as bait is prohibited.