Dick Sternberg warned of the threat zebra mussels pose to Minnesota waters.
Lake Mille Lacs, Minnesota's premier walleye fishing lake, might see an explosion in zebra mussels this summer, according to Dick Sternberg, a onetime DNR fisheries biologist whose report Saturday to the DNR Roundtable underscored the threat invasive species pose to state waters.
And it's a myth that zebra mussels don't threaten walleye and other sportfish populations, Sternberg said.
"Just look at Lake Erie and Lake Michigan,'' he said.
Zebra mussels suffocate and starve native mussels, said Luke Skinner of the DNR, adding, "They out-compete small fish for food and they impede recreation.''
Nineteen Minnesota lakes are infested with zebra mussels, along with the Mississippi, Zumbro and St. Croix rivers.
"We need a strategy,'' said Duluth conservationist Dave Zentner at the DNR meeting, underscoring the seriousness of the problem. "And we do need to find the dollars to find invasive species.''
Sternberg said the total poundage of baitfish in Lake Michigan dropped from 450,000 tons in 1989 to 30,000 tons in 2008, a record low, due to zebra mussels.
No one has found an effective, economically feasible way to stop the spread of zebra mussels. Notably, some large lakes in other states with limited access points feature decontamination stations that clean boats entering and leaving — Lake Tahoe being one.
Zebra mussels have a life span of two to five years. In their larval stage, they are microscopic, making them nearly impossible to detect on boats and motors as they are transported from lake to lake.
Jay Rendall, DNR aquatic invasive species prevention coordinator, said behavior changes are needed to prevent, or at least slow, the spread of invasives in Minnesota waters.
"But it can be like pushing a rope,'' Rendall said of implementing the kinds of changes needed by boaters and others.
Zebra mussels arrived in the Great Lakes as hitchhikers in ballast water of ocean-going ships.
On some Lake Michigan beaches, dead zebra mussels have washed up, creating impassable windrows a foot deep, Sternberg said.
Near Lake Huron, bait shops and motels that once catered to anglers have closed, Sternberg said, due to the effects on sportfish of zebra mussels.
Bob Meier of the DNR said the agency intends to heighten its education and enforcement efforts in an attempt to slow the spread of zebra mussels and other invasives.
"Some people have suggested we increase penalties'' for toting aquatic plants from lake to lake on their boat trailers, Rendall said.
Increased watercraft inspections also are possible.
Meanwhile, on Mille Lacs, a "huge'' increase in the number of mussels observed by DNR divers last summer sets the stage this summer for higher populations in that lake.