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Swanson's action thrusts Minnesota into the legal battle initiated last week by Michigan asking the U.S. Supreme Court to immediately order federal, state and local officials responsible for Chicago-area locks and waterways to take action to keep Asian carp out of the Great Lakes.
Ohio officials also have joined the effort. Wisconsin Attorney General J.B. Van Hollen is considering the situation. Under the U.S. Constitution, lawsuits between states are heard in the U.S. Supreme Court, which is expected to hear the case at a Jan. 8 conference.
"Proper stewardship of the Great Lakes means preventing an environmental train wreck caused by the introduction of Asian carp into the Great Lakes ecosystem," Swanson said in the legal brief.
Swanson's brief asks for closure of certain Chicago-area locks connecting certain Illinois waterways directly to Lake Michigan. The brief also asks that pumping gates be operated in a manner to prevent carp from entering the Lake Michigan. The states also are asking for new barriers to stop the carp.
Opponents say that closing the Chicago locks would cost hundreds of jobs. The American Waterways Operators, the national trade association for the U.S. tugboat and barge industry, last week said the closure would harm local businesses and the economy.
Asian carp were introduced to the U.S. to help keep private fish ponds clean. But they escaped during floods into the Mississippi River system in the 1980s. They moved up the Illinois and Des Plaines rivers to the Chicago area and are very near Lake Michigan.
The carp are voracious filter-feeders, sucking out small organisms from the food chain. They become the dominant species in areas they invade, and scientists are concerned they may displace native species. Some of the Asian carp species are known to grow to 100 pounds and jump up to 10 feet into the air when disturbed by a passing motorboat.
In November, DNA testing by the Army Corps of Engineers found that Asian carp probably have passed electronic barriers installed on the Chicago Sanitary and Ship Canal to keep them out of Lake Michigan. Illinois and federal officials earlier this month poisoned a six-mile stretch of the Chicago Sanitary and Ship Canal that runs between Lake Michigan and the Illinois River to kill any carp that may have passed the barrier. Only one dead Asian carp was found, but officials of other Great Lakes states also want the lock system closed to keep the fish out of the lakes.
Lake Superior area fish biologists say the carp probably wouldn't thrive in the cold, deep waters of Lake Superior, but probably would cause problems in the warmer, fertile waters of the Twin Ports harbor and St. Louis River estuary.