The Ohio Department of Natural Resources (ODNR) is reminding people that fish kills may be common in ponds and small lakes as the ice and snow of the past few months gives way to spring.
Winter fish die-offs caused by long periods of heavy ice and snow cover on small waters are referred to as winterkills. Winterkill is caused when persistent ice forms a surface barrier between the water and air that prevents circulation of oxygen and blocks sunlight. If these conditions continue long enough, the oxygen fish need to survive may be depleted and result in some or all of the fish suffocating. Lacking sunlight, plants stop making oxygen and eventually start to use it as they die and decompose.
Winterkill is most common in shallow ponds and typically results in dead fish being seen along the shore. Ohio’s northern counties are usually most susceptible to winterkill because of colder temperatures and more frequent snows, but this year, winterkill of ponds is possible throughout Ohio.
Some fish die-offs are expected in Ohio’s larger lakes as well this year, but for different reasons. Fish such as gizzard shad, which are less tolerant of long, cold winters, are commonly seen along the shorelines of reservoirs and even Lake Erie during moderate winters. However, in larger waters, the species that commonly die off following winter are resilient and return in great numbers following a single spawning season.
Unusual water coloration, strong odors or other unusual conditions may be indicative of non-natural causes and can be reported to the ODNR Division of Wildlife. Call 800-WILDLIFE to report a suspicious fish winterkill.