How Fish Survived the Winter
Ah, yes! Spring─ it’s finally here!
Trees are budding. Birds are chirping. Bulbs are blooming. Everywhere, new life pushes its way through earth and old leaves.
And at the lake, fish swim to the surface once again to kiss the face of the water.
But where were they this winter?
When the temperatures dipped below freezing, and the water in lakes and ponds, rivers, creeks and streams froze hard enough and thick enough to support not only the occasional scavenging deer, but also laughing hordes of skaters bundled up against the cold, how did fish survive beneath the thick layer of ice?
The short answer is that sometimes they didn’t.
Sometimes, fish freeze to death when temperatures drop. At below minus five degrees Celsius, ordinary, run-of-the mill fish—the sort that are not adapted to living under extremely cold conditions─ actually freeze to death.
Usually, however, fish live through the winter, in part due to their survival skills and in part due to the way that large bodies of water freeze.
Lakes and other substantial bodies of water don’t freeze solid. Only the top layer freezes. Below, oxygen and water, albeit cold water, provide a livable environment for fish and other forms of aquatic life during the winter months.
Some fish (certain types of cod, for instance) produce a substance called glycoprotein, which works like antifreeze does in a car. Just as coolant prevents engine and radiator fluids from freezing by lowering their freezing points, glycoprotein lowers the point at which a fish’s bodily fluids freeze.
Most fish, however, simply remove themselves to the still waters at the bottoms of lakes and rivers in order to survive the winter. There, where they are safe from predators and do not have to fight the currents, they can operate at a reduced metabolic rate until the weather and the water warms back up again.
In effect, because they are poikilothermic animals (that is, cold blooded) and have no means of warming themselves, fish hibernate until winter passes.
Because food is scarce in frozen lakes and ponds, fish are ravenous once the weather warms, and often, after surviving the vicissitudes of wintertime, they succumb to anglers and the lure of easy prey.