Question

In cold countries, the surface water or rivers and lakes freeze. what happens to the fishes living there?

Answer 1

I liked your question.

Here is the answer,
As you know, temperature changes as we go from top to bottom of a lake. The surface is much cooler than the depths. So, even when surface freezes, fishes and other creatures stay deep I side the lake. As temperature decreases, they go deeper and deeper to remain alive.

If the temperature is extreme enough, then the entire lake would be frozen. In such cases, aquatic life will die. However, we have not come across any of such situation till now.

Hope it helps !! ;-)

Answer 2

In cold winter months, lakes and rivers freeze over forming ice. Yet, fish and other aquatic animals manage to survive.

Animals like seals, penguins, walruses and a wide variety of sea birds are all fish eaters. They live in the Arctic and Antarctic Circle, amidst the icecaps. The land is completely frozen. Yet these animals manage to live in this region.The icy waters of the Arctic and Antarctic Oceans support a great amount of marine life. For millions of years life has remained unchanged, making it possible for these animals to adapt themselves to these particular patterns of existence.

Jellyfish: Fragile creature of the sea

But they do get some help from nature. All liquids have a boiling point and a freezing point. When water boils at a certain temperature it turns into steam. When it is cooled to a certain temperature it freezes and becomes ice. Water boils at 100 degree Celsius (100 °C) and freezes at 0 °C. When the outside temperature falls below the freezing point of water, lakes and rivers get frozen.

However, only the top layer of the lake or river freezes. Underneath the frozen upper layer, the water remains in its liquid form and does not freeze. Also, oxygen is trapped beneath the layer of ice. As a result, fish and other aquatic animals find it possible to live comfortably in the frozen lakes and ponds.