Rusty Crayfish: A Nasty Invader Biology, Identification, and
Impacts Rusty crayfish (Orconectes rusticus) have invaded much
of Minnesota, Wisconsin, Michigan, Illinois, Ontario, and
portions of 17 other states (Figure 1). Although native to the
Ohio River basin and the states of Ohio and Kentucky, rusty
crayfish continue to spread into many lakes and streams where
they cause a variety of ecological problems. Rusty crayfish are
probably spread by non-resident anglers who bring them along to
use as fishing bait. As rusty crayfish populations increase in
many areas, they are harvested for the regional bait market,
biological supply companies, and food. Such activities probably
help spread the species farther. Invading rusty crayfish
frequently: - displace native crayfish, - reduce the amount and
kinds of aquatic plants, - decrease the density and variety of
invertebrates (animals lacking a backbone), and - reduce some
fish populations. Environmentally sound ways to eradicate
introduced populations of rusty crayf