Lack of oxygen killing fish in Albert Lea lake Experts say "winterkill" event is a natural phenomenon. Posted: Feb 26, 2021 7:13 PM Posted By: Mike Bunge ALBERT LEA, Minn. – A lack of oxygen is killing the fish in Pickerel Lake. The Minnesota Department of Natural Resources (MNDNR) says such a “winterkill” event is caused when snow and ice on a body of water reduces the amount of sunlight reaching underwater vegetation. The Shell Rock River Watershed District says Pickerel Lake is shallow, so available oxygen can be quickly used up. Experts say winterkill is a natural process and help to thin out bodies of water that are overpopulated with fish. Craig Soupir, MNDNR Waterville Area Fisheries Supervisor, says this winterkill is great for the lake, given its water quality decline in recent years. Soupir says MNDNR plans to restock the lake with pike and perch in the spring of 2021.