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Invasive Crayfish Discovered in St. Louis Bay

Rusty crayfish (Orconectes rusticus) were found for the first time in the Duluth-Superior harbor at Minnesota Power’s M. L. Hibbard Steam Electric Station near the Bong Bridge in June. While inspecting for zebra mussels, Doug Jensen, Sea Grant Exotic Species Information Center Coordinator, and Eric Skadsberg, Plant Manager, collected four of these invasive crayfish from the screens that guard the plant’s water intake pipes.

“Rusty crayfish are aggressive, displace native crayfish, and can clear-cut aquatic plant beds,” said Jensen. “They can grow quickly, avoid fish predation, and are known to chase fish from nests then eat the eggs.”

Minnesota Sea Grant staff responded by sampling 80 locations throughout the harbor and up to the Fond du Lac Dam to gauge the infestation’s extent. They found rusty crayfish near the Blatnik Bridge and also trapped three native crayfish species, and nine species of fish. Three of those fish (round goby, ruffe, and threespine stickleback) were invasive exotics.

Selling live crayfish for bait or aquarium use is illegal in Minnesota. Live crayfish taken from a waterbody can only be used as live bait in that same waterbody, according to Minnesota Department of Natural Resources regulations. Wisconsin Department of Natural Resources regulations state that crayfish may only be used as live bait in the Mississippi River and the Great Lakes.

Jensen believes the spread of rusty crayfish can be prevented or slowed through education. He urges everyone not to transport or release crayfish. Boaters should avoid transporting aquatic plants, drain water from boats and motors, and discard unwanted bait on land.

“Once rusty crayfish gain a foothold there is no environmentally-friendly way to eradicate them,” said Jensen. “Preventing the spread of rusty crayfish and all the other aquatic invaders from the harbor is an essential part of protecting our inland waters.”

Rusty crayfish are native to the Ohio River Basin. This pest may have spread to Minnesota through ballast water discharge, live bait use by non-resident anglers, and releases by students or teachers after studying crayfish purchased from a biological supply house.

A fact sheet describing biology and impacts of rusty crayfish is available from Minnesota Sea Grant. Order a free copy of Rusty Crayfish: A Nasty Invader from our products list, look on the publications page and our free order form, under the exotics category, item X 34. For more information contact Doug Jensen at 218.726.8712 or djensen1@d.umn.edu.

By Sea Grant Staff
September 1999

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