Due to the severe weather of the past few months, our fisheries staff is reporting that "winter fish kills" may be possible at some Forest Preserve lakes and ponds. These kills are caused by heavy snow cover over thick ice, blocking sunlight from penetrating the water. The lack of light prevents the aquatic plants in the lake from producing oxygen. Reduced levels of dissolved oxygen in the water could result in the suffocation and death of fish. As the ice melts, the fish become more noticeable at the surface and along shorelines.