Add another sport to the list of winter leisure activities. A growing number of anglers have found they can fish for trout in winter.

Five years ago, fish management officials designated January first as opening day for an experimental nine month trout season for streams in southwest Wisconsin. The selected counties were Columbia, Crawford, Grant, Iowa, Lafayette, Richland, Sauk and Vernon. The boundaries of these eight counties enclose roughly ten percent of the state's total trout stream mileage.

They contain brown, brook and some rainbow trout. Browns are the most numerous, but there are good populations of brook trout in certain headwaters.

Trout require the coldest water of all our game fish. Wisconsin's only native stream trout, the brookie, needs the coldest and cleanest followed in order by the rainbow and brown.

In our relatively open country, trout streams are dependent on adequate spring flow to keep summer water temperature low enough for trout to tolerate. The same springs keep trout streams ice free, or nearly so, all winter.

Because trout are cold water fish, their metabolism isn't slowed as much by frigid temperatures as that of most others and they stay comparatively active and hungry in cold weather.

As water temperature approaches freezing however, their body functions do slow down. For instance, they are quite a bit more active at readings above 40 degrees than at 33.

Fish specialists tell us that all three species are most active and enjoy good growth within a temperature range of 45 to 65 degrees, with brown trout thriving best at the high limit and brook trout towards the lower.

Surface temperature of streams is closest to that of the air while the deepest parts are least affected by it. In other words, if a thermometer near a trout stream reads below zero, the top of the stream could be 33 degrees and the bottom of a pool might very welI be 40 or 45 degrees.

Trout are more comfortable at 45 than 33 degrees so they congregate at the bottom of pools with the largest occupying the deepest places.

They are fatty fish and so must have a large percentage of fat in their diet. In our area insects are the principal source of this fat. As an example, scientists tell us their studies show wild brook trout, year around, are dependent on land insects for one third of their food. These usually fall or are blown in the water from adjacent grass and trees. The balance of their diet is mostly aquatic insects and small crustaceans.

Large trout eat some smalI fish of course, but the need for the fat insects furnish is always there.

In winter, cold weather either kills terrestrial insects or drives them to cover. At the same time, activity of aquatic insects also lessens as hatches virtually cease. Water, that from early spring to late fall was teeming with drifting, swimming, rising, and emerging organisms of all kinds, becomes almost barren and trout have to scrounge in rubble and bottom vegetation to satisfy that hunger for insects.

A properly presented imitation is often more deadly than in summer. Try patterns that suggest caddis larvae. Mayfly nymph, gold ribbed hare's ear, black beetle, muskrat's regret, and silver nymph should work well. Fish them in the deepest part of the pools, just off the bottom.

As a rule, cold weather flies are darker colored than summer ones. It's a simple matter of nature using solar energy.

Mike Cufaude and I spent a forenoon in early January on a Grant county brook trout creek.

It was a beautiful stream that traveled through a succession of rapids and pools, down a wooded valley, then into a meadow. We fished the wooded area.

Air temperature was in the low twenties. It was a gray day, overcast with the kind of mist you expect to dispel by mid-morning but didn't. Hoar-frost was everywhere.

There were recent beaver cuttings. Their dams spanned the creek in a couple of places. The canals they used to float trees to the creek were frozen hard but the stream itself flowed as merrily as if it were summer.

Using silver nymphs, we took and released many nice brook trout. Because we were fly fishing, they were only lip hooked and easily returned unharmed.

Every pool produced fish and if we rested a pool for a half hour or so, we could return and repeat the performance.

It seemed like they figured our silver nymphs were just what was lacking in their diet.

After using up nearly a roll of film taking pictures of Mike catching trout, I said, "I think you're catching the same one over and over". He said, "No, I'm not, they aren't all the same size". We didn't keep any fish until time to leave. We took six home, between us.

The silver nymphs were size 14. It's a simple pattern with brown hackle and silver tinsel body. Mottled feather over and under-lays divide the hackle and leave a strip of tinsel exposed on both sides. It has a glistening, translucent appearance in the water.

We had 4X tippets about ten inches long tied to our leaders and the silver nymphs tied to them. We made an overhand knot in some lead wire around each leader just above the tippet. By pulling this tight enough so it couldn't slip past the tippet knot, we had a rig that would slide along the bottom and let the fly swim just free of it.

This is a quick, simple way to weight a leader when fly fishing without making casting difficult. If one lead knot isn't enough, It's simple to add >another. Split shot is almost always too heavy and an abomination to cast.

After the knot is tightened, be sure to break off the projecting ends. If you don't it will revolve in the water and twist your leader badly.