Every year the question arises about how fish survive during the winter, under the ice. The answer is that the fish are very adaptable to changes in their environment, but their environment doesn’t change as much as ours.
The temperature variances in the water world are only about 40 degrees all year, from 75 degrees in summer to 34-40 degrees under the ice. We see that in our environment in a few days.
Because fish are ectothermic, cold-blooded, their metabolic rate drops well below what it would be during the summer so their need for food and their digestion slow dramatically. When the water temperature is in the 70s, it may take a fish 24 hours to digest its prey; in the cold water that same prey might take a fish an entire week to digest.
Still, folks may wonder where the fish go and what they eat. Fish will locate where the water temperature is the warmest usually in deeper water where there is also more oxygen. When the late season “turn over” occurred on the lake the warmer surface water sank down and mixed with the cooler deep water.
The turnover also churned up the bottom, releasing a lot of food for the fish. Species like bluegills, perch and crappies feed on the immature larvae of large variety of aquatic insects that are found in the mud and muck at the bottom of the lake or pond.
Larger fish like northern pike normally do not feed on bluegills, because they are hard to swallow and are effective at hiding in the weeds, but during the frozen-water period, bluegill become a primary staple for pike.
As the winter progresses, the ice gets thicker, snow builds up on the ice, less sunlight gets through and oxygen levels fall. The fish adapt by slowing down even more, and some adapt better to low oxygen than others. This is the time of the year when winterkill occurs, a natural and beneficial process making for faster growth rates for the survivors.
We haw this occur at Lovelace Park a few years ago and all is well there.
The aquatic world has been adapting to change for millions of years and surviving in spite of our mistakes and pollution, living in a frozen water environment is just one more adaptation. Until next time … keep a tight line.