A survey by the Minnesota Department of Natural Resources completed this week shows the number of zebra mussels in one of Minnesota's most popular fishing lakes has gone down.
MPR reports zebra mussels in Mille Lacs Lake dropped from about 1,270 per square foot last year to roughly 1,070 per square foot this year, down more than 15 percent, the first decline since the invasive species was discovered in the lake in 2005.
DNR researchers tell MPR that it's not unusual for invading species to ramp up in big numbers and then scale back. More data will need to be gathered next year to determine if 2013 marks the beginning of a decline or is a one-time result of cold spring weather or other factors.
In addition to attaching themselves to boats and clogging motors, zebra mussels can cause major changes to the lake's ecosystem, creating a shift in fish populations.
"No one can blame what is happening in Mille Lacs Lake entirely on zebra mussels but it is unquestionably a major contributing factor in the collapse of the walleye and perch fishing there," said Paul Nelson, fishing guide and columnist for the Bemidji Pioneer.
There is no proven method yet to get rid of fast-multiplying zebra mussels once they appear in a lake, so officials say their best strategy for now is to prevent the invaders from appearing at all.
The DNR says nearly 150 watercraft inspectors are stationed around the state this summer to help stop the spread of zebra mussels and other aquatic invasive species.
Boaters are required by law to take extra precautions to avoid spreading invasive species or face fines.
Click here for a list of Minnesota's infested waters.