Winter Fish Kills 101

If you know people with lakes and ponds around Central Illinois, then odds are you know people who have had some fish die following this long, cold, snowy winter... I have been investigating fish kills pretty much daily for the last couple weeks.


Anyhow here is a summary of what goes wrong in the winter and also some answers to frequently asked fish kill questions.

When snow sits on the ice, it blocks the sunlight from getting into the pond. Without sunlight, there can be no life. When the sun is blocked for extended periods of time, the plants and algaes which normally give off oxygen, actually start dieing and using up oxygen.

Typically in winter fish kills the biggest fish in the ponds die first because they require more oxygen. Also not all areas of the ponds (especially irregular shapes) have the same oxygen content throughout. There can be some dead zones and some live zones in ponds.

Fish species that utilize the lower half of the water column usually also die first. Small fish less than 4" and crappies especially usually dont die unless the oxygen depletion gets real bad. Turtles and Dead Frogs are also a sign of a pretty bad fish kill.

Not all dead fish float!!! Sometimes they float for a day, sometimes 2 days, sometimes a couple weeks, and sometimes not at all or sometimes not till weeks later... I would investigate daily once ice comes off. Its actually pretty easy to miss a big fish kill.

Ways to prevent winter fish kill are to shovel snow off the pond in strips, drill lots of ice fishing holes every day, or get a lake bottom aeration system! With aeration systems we run them all summer long and that makes for a much healthier pond going into winter. Healthy ponds have much happier fish all winter long. I typically dont run aeration systems in the winter, but when snow builds up like this year, we turn them on during warmer days to open up the shallower areas of the pond.

I dont like to run aeration in deep water in the winter time. Ice is actually a good insulator for the pond. Its the snow thats the culprit. The water in the deepest part of the pond is 39 degrees and I dont like to push that nice warm water up to the surface and expose it to negative temperatures. That actually super cools the water. Winter aeration we run typically in the shallower portion of the pond.

I dont like for fish to just survive, I have found the key to growing really big fish is to have them thrive 365 days per year. Aeration systems really are the key to keeping fish happy in ponds during the heat of the summer and the snow of the winter.. Happy stress free fish grow into really big fish and create happy anglers.

A big mistake people make when restocking winter killed ponds is they restock large amounts of small fish... well let me tell you that is a big mistake. Typically the ponds are already full of those small sized fish and you need bigger fish to keep them in check or you will end up with a very out of balance fishery... Usually I stock back 10-15 adult bass per acre and 100-150 bigger bluegill per acre and thats it!

Fishing the next few years following a winter kill can be phenomenal or can be terrible, all depends on if you get the pond stocked back with the right sized and amount of fish to keep everything in balance! I can tell you that the biggest fish we shock every year are usually from ponds that had fish kills 3-4 years prior.

Anyhow hope that information helps answer some questions for some folks. I have been traveling alot the past month helping lake and pond owners across the midwest learn the secrets to growing big fish. Last week I was in Jessup, Iowa; Lincoln and Omaha, Nebraska; Rockport, Missouri; and today was in Alpha, IL.

Every place I go to, I try to learn something from. Anyhow I really think that over the next couple years these private bodies of water that we are "experimenting and learning from and sharing information with" are going to be producing fish that normally have been unthinkable to be able to produce in smaller bodies of water. In my opinion we have only just scratched the surface of possibilities with pond and fish management!

If there is one key phrase to remember in regards to growing big fish its this: Happy 365! If you can figure out how to keep your fish happy 365 days per year with no stress and lots of food to eat you will grow trophy fish....