Did my fish survive the polar vortex?

An extremely cold winter can result in fish mortalities in recreational fishing ponds.

The extremely cold winter may have resulted in a winter fish kill in your fishpond, Photo courtesy Michigan Department of Natural Resources.

The extremely cold winter may have resulted in a winter fish kill in your fishpond, Photo courtesy Michigan Department of Natural Resources.

This was the winter of the polar vortex. Extremely cold conditions along with heavy snow across the Great Lakes region made for a long winter. We, as humans, felt the effects of the brutal winter, but these same winter conditions can have detrimental effects on fish in recreational fishponds.

Michigan Sea Grant and Michigan State University Extension recommend that recreational fish ponds in Michigan have a minimal depth of fifteen feet that will assist fish in surviving through the winter months. It is important to have this depth in a recreational fishpond to help maintain an oxygen supply for the fish over the long winter months, especially if there is no new oxygenated water entering the system.

 What typically happens in the winter months is that fish will continue to consume oxygen in a recreational fish pond. When ice forms during the winter months, it blocks the entry of new oxygen from the atmosphere into the water. Snow will then accumulate on the ice. This will block sunlight from entering through the ice, and aquatic plants that typically produce oxygen when sunlight is available will now consume oxygen just as the fish does. In addition, dead plant matter decaying on the bottom consumes additional oxygen. Therefore, a defined amount of oxygen that is in the recreational fishpond at the beginning of the winter is continuously being used up as the winter progresses.

So how do you know if your fish made it through the winter in your pond? After the ice leaves, you should look on the surface for any floating dead fish. Many times, however, dead fish do not float to the surface, so in that case you should look through the clear water to see if you can see them laying on the bottom. The best way, though, to see if your fish survived the long winter is to try fishing for them.

If you determine that your fish did not make it through the winter, you should make plans to restock your recreational fishpond. If your pond previously supported bass, it is best to stock about 500 fathead or bluntnose adult minnows and, after they spawn, stock the bass. To stock your pond, use either 100 fingerlings (2 to 4 inches) per surface acre in July-August, or 25-50 yearlings (6 to 10 inches) per surface acre in April-October, or 6-8 adults of both sexes (over 12 inches) per surface acre in October or May.

If your pond previously supported trout, spring fingerlings (2 to 3 inches) can be stocked at 200-300 per surface acre in April-May. Fall fingerlings (5 to 6 inches) can be stocked at 50-150 per surface acre in September-October for initial stocking or restocking. Spring yearlings (6-7 inches) can be stocked at 50-150 per surface acre in April-June for initial stocking or restocking. Adult trout over 7 inches can be stocked at 25-50 per surface acre in the spring or fall for initial stocking or restocking.

Related Events

Related Articles

Related Resources