Hard winter takes toll on area fish populations

MONTGOMERY COUNTY — The winter that seemingly wouldn’t quit is finally beginning to show signs of weakening as the ice covering area lakes begins to retreat.

Now that the ice is going, the evidence winterkill in shallow lakes and ponds becomes visible as fish that died during the hard winter are found along shore.

The most recent report of dead fish was from the Anderson Area Ponds and Hacklebarney West, both in Montgomery County.

According to the Iowa Department of Natural Resources, winter mortality happens to varying degrees during most years but the long winter of 2009-2010 will have greater impact on some local lakes and farm ponds.

The all-of-a-sudden onset of ice back in early December, followed by a never-ending parade of snow storms shut out the sunlight, capping the oxygen level in the water.

“We monitored the dissolved oxygen in a couple Montgomery County ponds through the winter and found lower than normal levels and I expected to see a fair number of fish kills due to low dissolved oxygen levels after the long winter we had,” said Bryan Hayes, fisheries biologist with the Iowa DNR. “It is important to keep in mind that having a winter kill is not the end of the world. It usually only affects a portion of the fish population and the fish that remain will grow quickly.”

An unknown number of dead largemouth bass, bluegill, crappie and channel catfish died under the ice at the Anderson Area as well as Hacklebarney West. The cause: winter stress from low levels of dissolved oxygen.

The extent of the die off will not be fully known until later this spring or summer, when fisheries biologist can take an in depth look at the population during their annual fish population surveys.

“For the most part, we will allow nature to fill in any vacancies created by winterkill, but if there was a significant die off, then we may take action to help the lake recover,” Hayes said. “In private ponds that suffer winterkill it is important for landowners to verify what kind of fish survived and look for evidence of reproduction this summer. Specifically, look for largemouth bass and bluegill reproduction.”

Shallow lakes and ponds are more at risk to winter kill because of the reduced water volume. Viking Lake and Hacklebarney East are at less risk due to their larger size and water volume.