These fish require both cold and well-oxygenated water. During summer they seek refuge in the cold bottom layers where temperatures are less than 72 degrees F. Death results if the oxygen level there declines below about 4 ppm. Trout will also die in streams if they are unable to find cold spring water. Several stream trout mortalities were reported during the hot summer of 1995. A very unique type of fish kill is caused by a lightning strike on water.
Death occurs immediately.
Large fish, which draw more electricity than small fish, may be killed selectively. In conclusion, the risk of some types of fish kills can be reduced by keeping as many nutrients out of the water as possible. However, they are often not serious in the long run because lakes contain thousands of fish per acre. They may be thought of as nature's way of thinning out fish populations. Usually, fish kills indicate that the habitat is of marginal quality for certain species because of the broad range of weather conditions we experience in Michigan.