How do fish survive in frozen lakes?

Question

When winter rolls around and lakes and bodies of water freeze over, do they just swim normally in the freezing water? In backyard ponds, you need a pump to keep them alive, why is this different from a lake?

Answer 1

Lakes are usually deep enough that they don't freeze solid. Most here in WI will freeze maybe 12-20 inches, and lakes are usually MUCH deeper than 2 feet!

Answer 2

Ponds and lakes freeze from the top down, meaning that beneath the icy surface there is usually a layer of liquid water where fish swim.

Answer 3

Although it's true that the water does not freeze when it's deep, it may be close to freezing which could be bad for fish.  Many animals have s super cooling system in their bodies.  They have special proteins called glycoproteins that prevent ice crystals from forming in their blood.  This allows the blood to flow freely, so you don't need a pump or anything to keep them alive, as long as the water is deep enough and doesn't freeze over all the way, they will be fine.