One of the best spots for walleye fishing in north central Wis. is predicted to experience another fish kill this spring.
The Big Eau Pleine Reservoir in Marathon Co. saw thousands of fish die off in 2009, now it could happen all over again.
The reservoir's frozen and snow-covered surface prevents the air from mixing with the water and light getting through, meaning there's minimal oxygen for the wildlife below.
"So what happens is all of the built up material on the bottom starts to eat up oxygen and that's presently what we're seeing out on the Big Eau Pleine Reservoir," said Tom Meronek, a fisheries biologist with the Wis. DNR. "The oxygen is being depleted rapidly."
Oxygen levels taken last week were about one part per million, which is quite poor. They should be about five parts per million. The levels suggest the fish kill is not only likely, but that it has already started.
"We'll probably see fish die at the level back in 2009, which was, we lost a good portion of the population, our major game fish, our muskies, our walleye, our crappie population," Meronek said.
Around 70 percent of the walleye population was depleted in 2009. Fortunately, enough survived to rebuild the population, but it's still not back to where it had been, meaning this spring's kill could be detrimental.
"We're going to see another three or four years of fishery that is really poor," Meronek said. "There's not much there for anglers to use."
Meronek says it's difficult to prevent this oxygen depletion, but the DNR and the Wisconsin Valley Improvement Company is working to save as many species as it can.
"There's not much we can do at this point," Meronek said. "The only real option on the reservoir is to start up the aeration system that's been in place for 30 plus years. That was started in February. It opens up almost 3/4 of a mile of river, so we do have oxygenation taking place."