Why Fish Don't Freeze in Arctic Oceans

Fish, being cold-blooded, maintain body temperatures equal to that of the water surrounding them. The polar oceans are characterized by winter water temperatures of -1.4°C to -2.0°C (29.5°F to 28.4°F). Blood plasma of most fish freeze at around -0.6°C to -0.8°C (30.9°F to 30.6°F). Why, then, are there any fish in the Arctic oceans at all? (Whales and other warm-blooded ocean denizens do not have to answer this question.)

The answer, as given in the June 1982 issue of Arctic in an article by Garth L. Fletcher and co-workers, is that marine fish in the High Arctic have antifreeze in their veins--and that does not mean a nip of Old Granddad.

The Arctic sculpin, for instance, manufactures an antifreeze protein in its blood named, appropriately enough, glycoprotein. This depresses the freezing temperature of its plasma sufficiently to permit it to live in the winter Arctic waters without turning into the block of ice you'd expect to find in your freezer.

Interestingly, the plasma of sculpin in more temperate climates, such as Newfoundland, contains the antifreeze protein only during the winter months, while their cousins in the Beaufort Sea manufacture it all year 'round.