UPDATE: Thousands of dead fish lining Wisconsin shorelines

UPDATED Tuesday, April 29, 2014 --- 9:54 a.m.

ROME, Wis. (AP) -- Thousands of dead fish are washing up on the shores of some central Wisconsin lakes.

Wisconsin's Department of Natural Resources says the phenomenon is likely the result of thick ice that trapped fish in waters with low oxygen.

Daily Tribune Media reports (http://bit.ly/1rB4iJ6 ) residents near Lake Petenwell are seeing a second unusual sight -- pelicans have come to scoop up the dead carp and walleye.

The DNR expects the cold winter will result in more dead fish in lakes throughout the state. The department expects winter kill to be worst in shallower, backwater areas.

DNR Fish Team supervisor Justine Hasz says it's likely the pelicans are turning up because their normal staging grounds on Lake Michigan are still frozen.

Copyright 2014: Associated Press


Updated April 11, 2014 --- 6:36 p.m.

When winter comes, fish have less opportunity to get oxygen.

"It's like putting a lid on the lake so to speak -- a lid on the jar," said Paul Cunningham, a fisheries ecologist for the DNR.

When ice covers Wisconsin lakes, fish rely on photosynthesis from plants in the water to survive the winter.

"And then when you put snow on top of the ice, you decrease sunlight levels," said Cunningham.

He says it's the equivalent of "shutting out the lights" for fish and plant life underwater.

"Oxygen levels in the water column will drop and drop and drop -- to the point that fish, many of our sensitive species, can no longer survive," said Cunningham.

It's called fish kill, and it happens every year, but more snow and ice this winter means more dead fish on Wisconsin shores.

"Last year we have 12 to 14 lakes that experienced winter kill statewide, and we expect that number to increase quite a bit this spring," said Cunningham.

You won't see fish kill on bigger lakes like Mendota or Monona. It'll be on Wisconsin's shallower lakes that you'll see the dead fish wash up on shore.

It could mean good or bad news for anglers -- but that's up to mother nature at this point.

"Some winter kills can actually be beneficial in that a portion of the population survives and as a result they have more food available. Their growth rates increase and we see better size structure in some of our fisheries. In other situations it's not so beneficial."

Those other situations are invasive species -- often the common carp and black bullhead. They have a better survival rate with less oxygen, but it depends on the lake.

People will begin to see the effects of fish kill in the coming weeks as ice melts and wind blows any fish affected to shore.

If you see any dead fish wash up on shore, the DNR asks you to alert them by calling their tipline.

They rely on tips from the public to know whether fish kill is severe enough to re-stock the lake for anglers.

Posted: Friday, April 11, 2014 --- 7:13 a.m.

MADISON, Wis. (AP) -- The state Department of Natural Resources says people might notice more dead fish washing ashore in northern Wisconsin this spring.

DNR biologists expect see die-offs every spring. Ice and snow blocks sunlight from reaching oxygen-producing aquatic plants. As the plants they stop producing oxygen fish need. The DNR documented 18 fish kills caused by low oxygen levels last winter.

It's rare for lakes to see a total winterkill. Fish often seek out tributaries or springs where oxygen levels are higher. But the DNR says 3 feet of ice still cover many northern lakes and fresh snow that fell last week is making things even darker underwater. That could lead to larger die-offs.

DNR officials are asking anyone who happens upon a winterkill to contact the agency.

Copyright 2014: Associated Press

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