Written by Industry Expert Joe Holz, International Sales Manager at Kasco Marine
Winter fish kills are a serious threat to your fish population if you live in the north. If large amounts of snow and ice form on your pond or lake, it can block out sunlight from penetrating into the water. Without sunlight, plants die, thus ceasing to give off oxygen they would produce during photosynthesis. The dead plant material also provides added nourishment for bacteria which also use oxygen. As the winter progresses, the available oxygen in the pond can be used up to a point where fish can suffer.
In the winter, the metabolism of fish will slow down. They move less, eat less, grow less, and use less oxygen. The same goes for bacteria in the pond, the oxygen consumption is lower. However, oxygen levels can drop low enough to cause major problems in a pond if the winter is severe enough. In many cases, the larger trophy fish of a given species will consume more oxygen. Therefore, during low oxygen times, your biggest fish can die.
Luckily, winterkill can be prevented.