Spring kill Spring kill occurs in lakes and rivers when fish survive the winter but die as the water warms rapidly in May and June. It rarely claims many fish and is usually over in a couple of weeks. Spring kill is almost always due to natural causes beyond our influence. The usual victims are large bluegills and crappies, and other fish which spawn in the spring such as perch, bass, pike and suckers. A combination of stresses is usually responsible.
Fish come through the winter in a weakened condition because they've been eating at a reduced rate.
As the water warms, their metabolism increases and they divert much energy to strenuous spawning activities. Diseases and parasites also become more active and on a few occasions have been implicated in fish kills. Summer kill Summer kill occasionally occurs in lakes and streams during extremely hot summer weather. High temperature and low dissolved oxygen combine to stress the fish. Most prone to summer kills are pike, perch, suckers, bass, and bluegill living in shallow, productive lakes or bays with excessive amounts of algae or rooted aquatic vegetation.