INDIANAPOLIS (AP): This winter's frigid weather could cause an unusual number of fish kills, particularly in northern Indiana.
 
The Indiana Department of Natural Resources says there's ice up to 20 inches thick on lakes and ponds, not to mention record or near-record snowfall. The agency's fisheries biologists anticipate numerous fish kill reports after the spring thaw.
 
Fish kills are commonly caused by lack of oxygen. Some sunlight can penetrate clear ice and enable aquatic plants to produce the life-giving gas, but snow can block sunlight, cutting oxygen to dangerously low levels.
 
Once a winter kill starts, the DNR says there's not much that can be done. Drilling holes in ice won't help.
 
Shallow, weedy ponds are more susceptible to winter kills. Biologists don't expect big fish kills at deep lakes and reservoirs.