COLUMBUS – The Ohio Department of Natural Resources reminds Ohioans that small numbers of dead fish 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 from the past few months gives way to spring.

"Minor fish kills do not significantly impact fish populations or sport fishing opportunities in lakes and reservoirs," said Kendra Wecker, chief of the ODNR Division of Wildlife. "Fish kills are fairly common in Ohio, particularly right after ice-out, from late April through mid-June, and during prolonged periods of hot summer weather."

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.

Winterkills are most common in shallow ponds and become obvious when dead fish are seen along the shore. Ohio’s northern counties are more susceptible to winterkill because of colder temperatures and more frequent snows. However, winterkills are possible in any part of the state during winters of persistent cold weather and snow cover.

Fish die-offs are possible in Ohio’s larger lakes as well, but for different reasons. Some fish, such as gizzard shad, are less tolerant of long, cold winters and are commonly seen along the shorelines of reservoirs and Lake Erie during moderate winters. However, in larger waters, species that commonly die off following winter are resilient and return in great numbers following a single spawning season.

Concerned citizens should not attempt to rescue stressed or dead fish. Handling stressed fish significantly reduces their chance of survival. Go to wildohio.gov to find more information about fish and preventing winterkills. Large numbers of dead fish should be reported by calling 800-WILDLIFE (945-3543).

The mission of the ODNR Division of Wildlife is to conserve and improve fish and wildlife resources and their habitats for sustainable use and appreciation by all. Visit wildohio.gov to find out more.