BISMARCK, N.D. (AP) -- North Dakota wildlife biologists are asking anglers for help in documenting lakes that may have experienced winter fish mortality.
Game and Fish Department fisheries official Scott Gangl says some winterkill is expected every year, with the severity depending on winter weather conditions.
Winterkill happens when heavy snowfall blocks sunlight from going into lakes. Plants die and stop giving off oxygen, and they also consume oxygen as they decompose. That limits oxygen available for fish.
Gangl says the state had a colder than average winter, but about average snow cover. He says the lack of excessive snowfall means biologists don't expect widespread winterkill.
Biologists will begin sampling suspected winterkill lakes later this spring to document the severity of any die-offs.