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Thursday, March 31, 2011

Carp Explosion



Carp Explosion

By: Jeff Helsdon
Asian carp are at the gates leading to the Great Lakes, threatening its ecosystem and $7 billion fishery.

At press time, DNA testing indicates the invasive species, already established in the Mississippi and Missouri River systems, has breached the latest electronic barriers installed in the Chicago Sanitary and Shipping Canal. If true, only one navigational lock stands between them and Lake Michigan.

A concerted joint effort between the U.S. and Canada is underway. Rotenone, a lethal toxicant, was to be used in early December to kill fish in the section of canal by the electronic barrier, which will be closed for maintenance. The purpose is to drive fish back several miles until the barrier is operational again.

Approximately 20 Canadian Department of Fisheries and Ocean staff have been committed to dispense neutralizing chemicals. Technical support staff from Ontario are also being made available to assist cleanup. Quebec provided financial support.

Marc Gaden, communications director and legislative liaison with the Great Lakes Fisheries Commission, says this is an important step to assess how many fish are in the vicinity, but notes that this treatment is below the area where the latest carp DNA has been detected.

"That begs the question what happens next?" He says the only way to definitively stop the advance is to achieve "a permanent biological separation" by barriers such as lift locks or closure of access.

Gaden notes Asian carp were also detected in the adjacent Des Plaines River, which parallels the canal for 14 miles. As a result, the U.S. Army Corp of Engineers has been authorized to build a wall between the two waterbodies to prevent crossover during floods. Sand bags will be used temporarily. A study on how to obtain permanent separation is in process.

The consequences of Asian carp entering the Great Lakes are worrisome. Greg Conover of the U.S. Fish and Wildlife Service says they reproduce quickly, often becoming the dominant biomass in waterbodies they inhabit.

Gaden also pointed out that their presence would make recreational boating unsafe. Silver carp, one species of Asian carp, which easily reach weights of 30 pounds, are agitated by the sound of motors and leap out of the water. In one instance, a person knocked off a jet ski by a silver carp would have drowned if nearby boaters hadn't come to the rescue. Asian carp were brought into the U. S. in the 1970s to reduce algae in fish farms. It's believed they escaped during subsequent floods.

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