Msg 1 Posted: 08:38 AM 11/06/06 (CST)
Another one from the DNR...|
DNR kills off carp in effort to save Swan Lake
Tens of thousands of carp are dead and an important waterfowl lake is recovering from the fish infestation, thanks to a $160,000 chemical treatment performed by the Minnesota Department of Natural Resources.
Swan Lake in Nicollet County will be monitored this winter and spring to see if the fish-killing chemical rotenone was successful, said Ken Varland, DNR regional wildlife supervisor. The 3,000-acre shallow lake, considered one of the state's jewels for waterfowl, was treated Oct. 23 and 24 to kill an infestation of carp.
"It was more than I expected to see,'' said Varland of the number of carp and bullheads killed. "It was obvious they (the carp) had a pretty good reproductive year, especially in Nicollet Bay."
Carp, recently discovered in the lake, can be devastating to shallow lakes because they stir up bottom sediment and retard the growth of important aquatic plants. Wildlife managers were surprised when large numbers of carp were found in Swan Lake. The lake's water levels were lowered over the summer to help kill the carp and promote additional weed growth.
Two helicopters were used to spray 3,880 gallons of liquid rotenone over nearly 3,000 acres of water, making the Swan Lake reclamation one of the most complex the DNR has undertaken.
"We're extremely hopeful that the rotenone will kill the vast majority, if not all, of the carp that have been reproducing in Swan Lake,'' Varland said. "If any do survive, however, we're banking on Mother Nature to produce winterkill conditions that will eliminate them."
Varland said large numbers of bullheads and minnows also were killed during the treatment. Both species also are detrimental to shallow lakes because they stir up the bottom and eat aquatic insects that keep a lake's ecological balance intact.
The two-day treatment involved about 50 people. In order to get a complete treatment, advance Global Positioning System technology was used to map the lake and apply the chemical in appropriate amounts, Varland said.