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Out of Sight, Out of Mind

by Bruce Auchly - Region 4

Thursday, December 07, 2017

Ready for winter? Snow shovel out, snow blower gassed up?

If you are a bear, you eat a lot, then sleep for six months.

If you are a bird, you may either head to the sunny south or hunker down for a winter of birdfeeder visits.

But if you are a fish, then what? Ah fish, the forgotten animals.

Fish of Montana don’t go anywhere exotic in winter and don’t hibernate. Their behavior, however, may change with the seasonal changes in their habitat and food supply.

We tend to focus on, perhaps better understand, those animals we see. Think dogs and cats, deer, cattle and birds. Even if we cannot identify bird species, we see them every day and often we can tell the seasons by bird activities; they sing in the spring and migrate in the fall.

Fish, however, are out of sight, out of mind, which is too bad because fish are cool.

Although we classify fish as preferring warm-water or cold-water, all fish are cold-blooded creatures, ectotherms. They don’t have an internal furnace like a mammal that responds to the ambient temperature.

By contrast, mammals are endotherms, warm-blooded. We control our body temperature by mechanisms like sweating to cool off or shivering to warm up.

Having the ability to control one’s body temperature would seem to be a tremendous advantage, but that power comes with a cost. Maintaining warm blood means consuming food more often, stoking the internal furnace.

Fish can go for long periods, even months, between meals and expend less time and energy eating.

So how is it that certain fish species seem to be more active in the winter; fish that anglers tend to seek out and catch when ice fishing. Species like: walleye, northern pike and perch.

Part of what’s going on here is habitat and behavior.

In the winter, warm-water species like bass and crappie (neither are native to Montana waters) become more territorial, they don’t move around much. They wait for food, like small fish or insects, to come to them.

They are not impossible to catch when ice fishing, but you better drop the bait right in front of them.

Cold-water species like northern pike, perch and walleye will move around much more in the winter searching for food.

And then there are trout, which may or may not swim around much depending on their habitat and food supply.

Rainbow trout in a mountain stream, which has ice forming on the water surface and stream bottom, will hunker down and move little.

Their winter habitat has shrunk as has their food supply of insects. That’s why they can go months without eating.

Rainbow trout in a reservoir or lake will continue to swim around looking for food, though in the winter that might be plankton rather than insects.

Being cold-blooded works for fish. Think of that the next time you use the term cold-blooded as a negative phrase.

If you call someone cold-blooded, or say something makes your blood run cold, you may have just insulted a fish, which is not cool.