An icy world presents fish with special challenges

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The recent arrival of cold weather has resulted in ice forming on many of our lakes and rivers. While conditions are still dangerous on some waterways it won’t be long before we can head out after smelt and trout.

Fish have special challenges facing them during the winter. As cold-blooded animals trout and salmon slow down when the water cools and, although warm water temperature in the summer are much more critical to fish survival, the winter months also bring their own special challenges.

While we take ice for granted, for organisms that live in water there are actually several forms of ice they must contend with. On still water, such as lakes, surface ice forms fairly quickly when the water temperature drops below freezing. A cover of ice, especially if it is covered with snow, acts as an insulating blanket and ensures water temperature below the ice remains around 4C. One problem that may occur with ice cover is that no oxygen exchange takes place, and in small, shallow ponds prolonged period can result in winter kill where fish and amphibians, such as frogs, die from lack of oxygen.


Trout and salmon have evolved to survive winter conditions by finding habitats where they can survive with a minimum of energy. Young salmon, known as parr, find shelter down in the gravel, often behind large rocks, which protect them from the current. Brook trout, as well as slink salmon, are more likely to be found in deeper pools or still waters where they can remain out of the main current.

In the spring, summer and fall, fish are constantly looking out for predators from the air or land. Kingfishers, osprey, herons, cormorants and eagles all fish. In the winter fish can forget about winged predators but the land based ones are still around. Mink and otter are active during the winter and you can often see their fishing stations at the edge of lakes and streams.

Tight Lines.

Tip of the week:

The Red Cross recommends you require a minimum of 15 cm (six inches) of ice for one person while a group of people will require a minimum of 20 cm (eight inches). Snowmobiles need 25 cm (10  inches) of ice before they venture out.


Geographic location: Cape Breton, Pictou

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