Harsh winter could mean more fish kills

File photo. (Jessica via Report!t)
File photo. (Jessica via Report!t)

Owners of shallow ponds and lakes, especially in northern Indiana, should watch for fish kills this spring according to the Indiana Department of Natural Resources.

Considering the record or near-record snowfall and ice up to 20 inches thick on lakes and ponds, Indiana fisheries biologists anticipate numerous reports of fish kills once the bodies of water thaw.

The most common cause of fish kills in Indiana ponds is lack of oxygen.

Aquatic plants can produce oxygen only when sunlight is available. While some sunlight can penetrate clear ice, snow can block sunlight, resulting in dangerously low oxygen levels.

Shallow, weedy ponds are more susceptible to winter kills. As aquatic plants naturally die during winter, plant decomposition consumes oxygen that fish and other aquatic life need. Once a winter kill begins, little can be done to stop it. Drilling holes in the ice will not help.

Pond owners who experience a fish kill or need advice on other pond-related issues can refer to Indiana’s Pond Management Booklet at wildlife.IN.gov/3356.htm.

Biologists do not expect significant fish kills at deep natural lakes and reservoirs. The exception could be winter kills of gizzard shad, a species that is vulnerable to prolonged cold weather. Because the species is prolific and fast growing, shad losses do not have a lasting impact on shad populations.

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