The mountain men trapped beaver in the valley 150 years ago, and although they left no trace, the beavers have. The meadows on the valley's edge were partly built by the beaver and the broad marsh in its center was formed from beaver ponds that collected silt from miles of mountain creeks.

In dry summer the creeks appear to carry no silt at all, but when the high snows melt or the canyon thunderstorms gather, the creeks run overfull and brown with earth and the beaver ponds catch it, filling slowly to be abandoned by their engineers. The beavers build higher up, or lower down, and they build almost everywhere--Michigan, Maine, or Colorado. They are a blessing or a curse but their ponds are a way of fishing from coast to coast. They're most spectacular in rough country, but are often equally trout-filled where the streams are slow and where new dams drown the brush that lined the meadow creeks.

You'll hear of the "little brookies" in the beaver ponds and there are ponds where they are tiny; victims of the brook trout's way of overcrowding. Sometimes the Western ponds contain little cutthroat instead of the brookies, sometimes they have little browns or rainbows--and sometimes they have big trout of almost any kind.

Beaver ponds can bring depth to a shallow creek that could support a few or no trout without them and they can support healthy fish in deep water beneath heavy ice. At other times and places beaver ponds can become shallow and spread a cold brook into silted flats, defenseless under summer sun. Then the water becomes too warm for any trout at all. Or it freezes solid.

The beaver have not figured out these things, or if they have they are not interested in trout or trout fishermen. To them trout are an unused by-product of their construction projects.

A series of ponds coming down from the high country can be good for fishing in some spots and bad for it in others, and it can condense several kinds of fishing into a short afternoon's hike. Sometimes there will be a big super-beaver-dam with a shallow, silted marsh above it containing runty little fish that will charge anything they might be able to defeat. Below it might be a stretch of deep, slow current where a careless step will send startlingly large shadows darting beneath undercut banks.

So to say you have been "fishing the beaver ponds" will mean something different to almost every angler and is about like saying you have been "fishing a trout stream." Beaver-pond residents range from gluttons who gulp Muddler Minnows a third their size to persnickety veterans who push up cautious swells beneath #20 duns and flee from the first kinky leader.

You can learn a chain of beaver ponds and then learn anew from repeated trips. Beaver ponds, of course, are the big rodent's intrusion upon the more conservative forces of nature. You can sometimes stand on a rock-steady dam that forms a perfect casting platform. You can also damn near drown yourself in a sort of silt, water, willow, and alder man-trap that seems to serve no purpose to the beaver other than building practice, since he has abandoned the mess and built his house somewhere else.

Beaver-pond fishermen tend to become explorers, especially in valleys where the beavers have been perennially busy. Inexperienced beaver-ponders are likely to try one or two pools, and if the fishing is poor they decide it's probably the same on up the creek, but there are good ponds and bad ponds, sometimes for reasons I cannot fathom, and I am forced to fall back on chance for answers. Maybe the good fish just happened to be caught in this pond and never were able to work into that one. Maybe they have been eating overcrowded runts in this pond or reproduction must have run away in that one. A scientific approach ruins the fun anyway.

Beaver-pond fishing isn't considered very technical in most circles. The late Dan Bailey, the fly maker, was an inveterate beaver-pond seeker. He was capable of the most delicate approaches with the smallest flies, of course, but confessed most of his beaver-pond triumphs were over less selective fish. I am almost embarrassed at the number of times I have followed him to beaver ponds he had located through exploration and that I had reached through slothful mimicry.

There is one creek in mid-Montana so overshadowed by bigger water that only a few years ago there was but one set of wader tracks in its marshy spots. They were Dan's and I got there a week after he fished it, following his directions.

On one side of the creek is a pine ridge with a little rimrock and on the other side is a pastureland bench with a good view of the whole valley. The tepee rings are on the bench; neat circles of stones laid out to form an Indian village, the only sign of the hunters and fishermen who lived there before the brown, rainbow, and brook trout were brought to the nearby Smith River. If you will climb up to the tepee rings you will see much of the little creek and can figure a route to the beaver ponds and avoid being trapped in the marsh. The creek and its ponds have a wide strip of willows and the grass is lush on both sides.

When I worked up the creek below the dam I used a Hairwing Coachman with a little seven-foot rod that would stay out of the willows as long as I watched my short backcasts. Most of the fish were rainbow that lived near the heads of the pools. The big dry fly would come down the chattering little runs looking enormous. Then, as the fly reached where the rough water flattened, you could almost foresee the strike when the fish would come from the deep side under the willow roots. In the wide, slow places the creek would be 10 or 15 feet wide and if the biggest fish were no more than a foot long I could still be happy, for the scene was reduced to miniature and a king salmon would have been out of place.

The big dam was higher than my head as I came up below it. Water gurgled through it well down toward the base but it was fairly new; a product of beaver over-achievement, apparently thicker than need be.

When I cautiously put my head above the dam a family of mallards slapped and quacked their way into the air off to one side and I involuntarily ducked a little. The pond was more than one hundred feet long and almost filled with drowned willows. The original route of the creek was a slightly curved path through the brush and as I assessed the water there was a subtle movement in the willows--too big for a 10-inch fish--just a slow bulge.

The wind whistled downstream but I had backcasting room and I threw the fly into it. The leader crumpled awkwardly but my effort was not a complete failure and the fly landed sloppily at about the middle of the old creek channel. Two fish came for it and I landed a brilliant rainbow, thick and small-headed. Once hooked, it stormed across the surface, leaving patches of bubbles, and although I supposed the fishing was over for the time being, I slapped the fly back and caught a brook trout some 14 inches long. I also caught a smaller brown trout. If I could have raised a cutthroat it might have been a sort of poor man's grand slam but I was satisfied with three fish, headed for the next dam and went in over my waders.

The beaver dam was breached two years after I followed Dan's trail, a spring freshet being too much for it. But it had begun to collect silt anyway and the beavers or their descendants have built new dams farther upstream, one of them a disgrace to the beaver clan. It leaked and broke at one end, but the water rounded it in a curve and dug a shady hole against the bank. When I floated the #14 Cahill across that hole in another year a brown trout took it and tangled me in some roots.

Over at Bangtail Creek the brush was thicker and the stream went through chokecherry patches and rosebushes to where the beaver ponds, acres of them, spread broadly, reflecting sunlight in patches. I'd seen the wakes of startled fish one fall as I'd hunted ruffed grouse there and we worked hard to get room for even a roll cast. We'd planned the trip for a year. The fish came but they were six-inch cutthroats and we gave up after an hour or two and trudged out. I suppose if the fish had to be small it's better that they were "natives."

They've probably been there since before the tepee rings were laid over near Smith River.