Fish Winterkill May be Common as Ice Retreats from Ohio’s Ponds and Lakes

COLUMBUS, OH – The Ohio Department of Natural Resources (ODNR) is reminding people that fish kills may be common in ponds and small lakes this spring. Winter die-offs of fish that result from long periods of heavy ice and snow cover on small waters are referred to as “winterkills.” Winterkills may occur in some Ohio waters this year as ice and snow of the past few months gives way to spring.

Winterkills are caused when persistent ice forms a surface barrier between 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 them suffocating. Lacking sunlight, plants stop making oxygen and eventually start to use it as they die back and decompose.

Winterkill is most common in shallow ponds and will become obvious if dead fish are seen along the shore. Ohio’s northern counties are most susceptible to winterkill because of colder temperatures and more frequent snows. However, similar to last year, winterkill of ponds is possible in any part of the state due to persistent cold weather and snow cover.

Some fish die-offs are expected in Ohio’s larger lakes as well this year, but for different reasons. Fish which are less tolerant of long, cold winters, such as gizzard shad, 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.

Go to wildohio.gov to find more information about fish and preventing winterkills.