Features of the behavior of fish in winter?

Although it seems to us that it is very difficult for fish in winter in winter, this is not so. Fish are cold-blooded animals. Accordingly, they do not need warm water. The main thing is that it should be above zero. Although ice covers water bodies, fish swim calmly on the bottom of water bodies. The only problem that can arise is a lack of oxygen. But fishermen leave ice holes, thanks to which oxygen gets into the water. Fish also get food in winter, although they are limited in movement due to the smaller volume of liquid water.