Spring and summer fish die-offs happen occasionally, and we are getting widespread reports of dead fish following the recent prolonged stretch of hot weather.
In mid-spring and summer, fish die-offs are often the result of warming water and opportunistic infections that spread in fish populations that are already stressed after the spawning season. Species commonly observed in these die-offs include sunfish, crappies and bullheads, and, occasionally, largemouth bass and northern pike.
If you encounter a large group of dead fish in a lake or a stream, please report them. Calling in a report provides a single point of contact for the incident. An early report also allows timely water sampling or other response actions, if needed. It’s especially helpful to know what fish types and sizes people see in a fish die-off.
More details: DNR fish die off page