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How Fish Survive The Winter

Did you ever wonder how fish stay alive after winter when the whole lake is frozen? Did you know the science behind it?

In winter most lakes in the arctic region are frozen. But when the winter passes the ice melts and we could see the fish. If the lake is frozen during the whole winter how did fish survive?

Photo by Harrison Haines from Pexels

Yes, During the winter lakes are frozen but not entirely. Only the top layer of the lakes freezes leaving the underneath water in liquid form.

Science behind this phenomenon

Every substance on earth has a boiling point and a freezing point. The volume of that substance changes between these two temperature point. Same goes with water. The boiling point of the water is 1000C and the freezing point of the water is 0oC. So technically the water should have the highest volume in 1000C and the lowest volume in 00C. But that statement is not true when it comes to water. The highest volume of water is at 1000C but the lowest volume of water is not at 00C. Water meets its lowest volume in 40C.

When the temperature of the water is decreased over 40C then the volume of the water is increased. When the volume decreases the density increases. That means The water at 40C is heavier than the water in 30C or 50C.

When the atmospheric temperature decreases during the winter the temperature of the water decreases. When the temperature of the water hits 40C then the water becomes heavier and sinks down the lake. Then the top layer which is hotter starts to cool down and when the temperature of that layer is deceased to 40C the water again sinks down. So always the water in the bottom is 40C. Eventually the upper layer of the lake is frozen and makes a slab of ice which has lesser density than the water. So the ice slab floats on the water and the water underneath stays in liquid form. And ice is not a very good conductor of heat so that the water underneath does not get frozen easily. The temperature decreases but it is a very slow process.

Also because of the ice layer the oxygen is trapped making it is easier to marine life to breath.

Now you know that the water in a lake does not completely frozen and even the oxygen is available. And that is how fish in the winter survive. It is obvious that the fish in these lakes have adopted to low temperatures like 40C. Otherwise even with these favorable conditions fish cannot survive the winter without those adaptive features. In the winter food is very hard to find. Many marine species grow slowly so that they would not need much food.

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