The lake freezes in winter, won't those fish freeze to death?

Usually not. But there is a premise that the water in the lower layer will not freeze and the fish will not freeze to death. When the water layer is shallow or the temperature is extremely low, the water below will freeze, and then the fish will freeze to death. Fish are mostly cold-blooded animals, and their body temperature will change with the water temperature.

Fish are mostly cold-blooded animals, and very few are warm-blooded animals. They breathe through their gills and have jaws and fins. The existing fish can be divided into two categories: cartilaginous fish (such as sharks) and bony fish (fish with linear fins and wavy fins).

Both groups of fish first appeared in the early Devonian. A more advanced group of linear finned fish, called bony fish, began to evolve in Jurassic and has become the most individualized fish. There are also several extinct fish.

Extended data:

Fish's appendage is fin, which is an exercise organ for swimming and keeping balance. Fins are composed of branch fins and fins, which are divided into two types. One is horny fins, which have no segments or branches and appear from the epidermis, and are found in cartilaginous fish.

The other is scale fin or bone fin, which comes from scales and is segmented, branched or unbranched, and is found in bony fishes. Fins are connected by thin fins. Bone fin can be divided into two types: fin thorn and soft thorn. Fin spines are formed by the deformation of a fin. They are hard spines that are neither branched nor segmented, and are only found in higher fishes.

The soft strip is soft and jointed, and its distal branch (called branched fin) or unbranched fin (called unbranched fin) is formed by merging the left and right halves. Fins are divided into odd fins and lateral fins. Lateral fin is a pair of fins, including pectoral fin and ventral fin, each with 1 pair, which is equivalent to forelimbs and hind limbs of terrestrial vertebrates.

Odd fins are unpaired fins, including dorsal fin, caudal fin and gluteal fin. The basic function of dorsal fin and gluteal fin is to keep balance, prevent tilting and swaying, and help swimming. Like a rudder, the tail fin controls the direction and pushes the fish forward. Common fish have the above five kinds of fins, chest, abdomen, back, buttocks and tail.

But there are a few exceptions, such as Monopterus albus without lateral fins, whose odd fins are also degraded; Eels have no ventral fins; Electric eels have no dorsal fins and so on.

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