Home Fish Facts Can Fish Survive Being Frozen? (3-minute Read)

Can Fish Survive Being Frozen? (3-minute Read)

by gvald

When it is cold, lakes, canals and rivers can also freeze over and become covered with a large layer of ice.


This brings us to the question: how do fish survive the winter without freezing?

This is the question that nobody asks, but it introduces one of the (many) peculiarities of water compared to almost all other liquids.

Generally speaking, the density of a liquid varies with temperature.


Can a fish survive after being frozen?

The answer may surprise you, but yes, it is possible, however, the probability of this happening in the wild is very small.


Already, a fish is very rarely frozen. To ensure its survival, it must not stay frozen for long, a maximum of 10 minutes, otherwise, some of its organs will not function at all, even after being thawed at 100%.


This phenomenon is comparable to the transfer of organs in humans, if the organ remains too long “disconnected”, it is impossible to put it back in circuit.


How do fish survive in a frozen lake?

In a lake where the layers of water are stacked by density, the bottom (the densest) is at 3.98°C. In winter, the less dense 0°C water rises to the surface and freezes, forming a layer of ice that covers the lake.


Furthermore, and this is true for all liquids, when a material becomes solid, it releases a large amount of heat called latent heat (this is what is used in pocket heaters). This heat goes into the water and prevents the whole river from freezing at once. This is also what allows the frozen lake to remain globally between 0 and 3.98 °C for several months while the air can go down to -10 or -20 °C.


The fish survive by staying at the bottom of the river, where it is 3.98°C.

In summer, the opposite happens: the densest bottom is still at 3.98°C, but the layers above are warmer (also less dense). Again, the fish will prefer to stay at the bottom of the river where the temperature is stable.


The fish have therefore throughout the year, at the bottom of the lake, a region where the temperature is constant and obviously always liquid.


Can fish in the ocean freeze?

No, this will not happen, since the water in the sea and oceans does not freeze, we explain why:


The freezing temperature of water-that is, fresh water-at rest is 0°C. The freezing temperature of sea water, on the other hand, is below 0°C and varies with the degree of salinity. The higher the degree of salinity, the lower the freezing temperature.


For water to freeze and form ice, it must first be cooled to its freezing point. Such cooling involves a loss of heat.

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