I’ve heard the term “winter fish kill.” What is it and why does it happen?
Linda - Stockbridge, MI
A winter fish kill occurs when your pond or lake becomes uninhabitable for aquatic life and a large number of fish pass away. Winter is the most common time for a fish kill because the long, harsh conditions of the season deplete the oxygen content of the water.
Prolonged ice cover on your pond or lake seals off the water from the air and prevents oxygenation of the water. Ice and snow cover also prevent sunlight from reaching your pond plants. Pond plants normally produce extra oxygen for your pond via photosynthesis. Finally, decomposing organic matter in your pond releases toxic gases that can’t escape from under the ice.
Eventually the competition for the limited supply of oxygen in the pond becomes too great. The fish suffocate and a winter fish kill occurs.
The good news is that winter fish kills are preventable. There are many things you can do as a pond and lake owner to maintain proper oxygen levels in your pond. First and foremost, invest in a good Aeration System. Aeration is the process of circulating air through water and it’s critical for overall pond health. A second option is to add beneficial bacteria products like MuckAway™ or PondClear™ to your pond or lake before the winter season. Beneficial bacteria digest accumulated decomposing organic matter in your pond and convert it to a harmless, odorless gas.
Pond Talk: What fish behavior may indicate low oxygen levels in your pond?