Rainbows and cutthroats share many characteristics. They are both spring spawners, which could occur any time from February to June, depending on water temperatures. They share similar thermal preferences, meaning that in waters supporting both species, they prefer the same water temperature.

In moving water, they are both drift-feeders. They take and hold feeding positions where there is some structure, like a rock or blowdown, to break the current. In still water, they cruise looking for action, like teenagers on Friday night. “Action” to a trout means anything that looks like or acts like food that they can fit into their mouths. Young trout mostly pursue aquatic insects, small crustacean and annelid diet until they get big enough to add forage fish.

WINTER WATER
TEMPERATURE
As every angler knows, fish are cold-blooded creatures. Biologists like Chad Jackson, of the Washington Department of Fish and Game, know that fish are poikilothermic. It’s a $25 word that means the fish’s body temperature varies with changes in the water temperature.

Fish don’t generate any body heat to stay warm in cold water. Instead, cold water causes a couple of reactions. As the water temperature declines, so does the fishes’ body temperature, and their metabolism slows along with their activity.

The decrease in metabolism then slows the digestion of food. Fish eat less at any one time and take longer to digest each meal.

February anglers should take an interest in all this biological talk because it should change the way you fish cold water. For one thing, facing cold-water conditions, you’ll need to present your offering to as many fish as possible in the hopes of finding one that has finished digesting the last meal and is ready, willing and able for more.

Most cold-water fish aren’t actively feeding most of the time: They are more interested in conserving energy.

Cold water also causes fish to seek water temperatures closer to optimum. In rivers, this may mean hanging out near the mouth of a small feeder stream whose water is warmer. Fish may move from the shady side of the river into the sunny side to take advantage of water that may grow a few degrees warmer by midday.

The sunny side may have the added benefit of prompting brief hatches of insects like chironomids, blue-winged olives and early March browns.

One river I fish in Washington has fabulous but short-lived blue-winged olive hatches in February. It brings the river alive with rainbows.

A favorite Oregon river always gives up February rainbows on bright, sunny days, even when the water is 41 degrees.

The Northwest typically gets a week or so of warm, dry weather that is perfect for fishing. It’s not so hot that mountain snow melts and blows out the rivers, but it’s warm enough to cause the water temperature to spike upwards a few degrees, and the fish respond by feeding actively.