With the onset of winter in reservoirs undergoing big changes, which affect the behavior of underwater inhabitants. The water temperature decreases. Gradually decreasing the light period of the day. Then the waters closed ice cover, top it fills up the snow - illumination falls even stronger. A long 4 months underwater inhabitants exist in conditions of cold, lack of oxygen and the semi-darkness. In wintering fish is sharply reduced activity almost completely stopped eating, retard growth, reduced heart rate, slow response to stimuli, the rate of metabolism in the body slows down and is supported by accumulated summer fat reserves.
Different species of fish varies blog this difficult period. Many thermophilic species of fish, such as bream, carp, tench, already in October-November gather in huge flocks and sent to the wintering holes. Here they spend about 3 months almost without movement, like herrings in a barrel! Those fish that are at the very bottom, even formed the sores on his belly.
The fish of the same species and age overwinter together in large clusters. If the pit is small, there are arranged identical individuals! Ichthyologists scientists explain this mystery of nature that mass concentrations of fish of the same species and age provides them with optimal conditions for wintering, because the metabolic processes in the body of the fish while less intense than it would be if fish wintered alone. In addition, more rational use slime that fish produce as an insulating means.
But soma attached above, about wintering holes on the outputs from the depths, the boundaries of the pits and enhancements bottom. This is because in the pit after only a month after the formation of the ice cover oxygen regime change dramatically for the worse that soma not tolerate.
As winter predatory fish
Fish predators in the wintering holes are not hiding. But the inhabitants of such pits for some reason do not touch, although it could be so for the whole winter to secure a full existence. The majority of pike, perch and pike hunt for those fish that ice shell above the head is easy and they do not go away for the winter with the usual habitat is perch, roach, bleak, verkhovka and ruff.
With the advent of the ice cover is changing the behavior of predatory fish. Predatory fishes are divided with respect to the light: so, the bass is twilight-day predator, the pike - twilight, pike - globalsummary.
In early winter under the ice creates a glare, which is “at hand” twilight predators. And then they are in the early days of the establishment of the ice cover suit their victims of the carnage. This biting predator called “pervalidus”.
But for burbot it, winter is a good time of the year. Warm summer water it depressing. At temperatures above 15-16°C burbot stops to eat and falls asleep, huddled in coastal burrows under large rocks or snags, and at a temperature of 27°C dies. Only in autumn, when the water is noticeably colder, he awakens and begins actively feeding. To hunt fish prefer the night. Young fish feed on zooplankton, and one-year-old move on "fish diet." When you break out the frosts and rivers covered with a thick layer of ice (in November-December in the North or in December-February in the temperate zone), burbot becomes more active and begins to reproduce, vymatyvat their eggs on the rocky parts of the bottom.
The fish migration
Some fish temperate and Arctic latitudes don't want winter to change their usual way of life. They prefer to move to warmer waters. Hamsa living in the Azov sea, they feed intensively in the summer, accumulating fat. With cooling water, it migrates through the Kerch Strait in the Black sea and winters there, plunging to a depth of 100-150 m during wintering migration of the Azov anchovy starts fishing for this fish. Caspian herring migrate in winter to the South, where the water is warmer.
And if the pond is shallow, stagnant and freeze in winter through? Such lakes exist in the Arctic. Their inhabitants - common carp and black fish Blackfish with the onset of winter, bury themselves in the mud. When such ponds freeze to the bottom, fish is often frozen in the ice. But their resistance to low temperatures is amazing. Even trapped within the ice, the fish do not die unless you freeze the gills and the liquid environment of the body. In the spring, when water is thawed, Blackfish comes to life during the short polar summer time feeding and leave offspring.
And this happens...
In Equatorial waters, where it is never winter, the fish can be active all year round. However, some of them in the winter months, too, the problems begin. Only they are connected, of course, not with cold, but, on the contrary, with unbearable heat and drought. Some tropical fish bury themselves in the mud and fall asleep. It helps them to endure the heat and the associated lack of oxygen.
If bream and Blackfish - the most hardy freshwater fish, little fish from the kind of corpozulia - Cyprinodon macularius (cyprinodon macularis)living in the South of North America, the record for maintaining the highest water temperature. She lives and manages not boil in hot springs California, water temperature which is 52°C! For reference: in the water with this temperature it is impossible for a long time to hold your hand.