ON THE BRULE RIVER, WIS.

Like great artwork continually in revision, this river has retained its graceful lines forever, while also changing -- if not its actual course, then its riffles and pools, colors and cadence.¶ Precisely because he appreciates such changes, and is drawn to them, Dave Zentner, of Duluth, loves rivers, the Brule in particular. ¶ Come winter, he might be seen alongside it, on snowshoes. In summer, he paddles it in a canoe. And, as on Wednesday, he fishes it whenever he can. ¶ "There's a hen making her redd right there," Dave said, pointing his fly rod to a shallow spot, midstream in the Brule. The day was atypically warm for late March, even hot, and we were looking for steelhead, migratory rainbow trout that live dual lives, for long periods swimming here in the Brule, while also, alternately, living in Lake Superior.

About 8,000 of these fish swam up the Brule last fall to over-winter in the river before spawning now, in spring, then returning to the big lake.

Mysterious fish, steelhead depend on rivers like the Brule, on which there are no dams or natural barriers to upstream migration. Steelhead here depend also on the pristine and wildly varied northwest Wisconsin watershed that gently cradles the Brule and its tributaries, like a mother might her baby.

Dave waded into the river, his fly rod in hand. Like many North Shore steelheaders, including those who fish Minnesota streams north of Duluth, his reel was spooled not with fly line but monofilament. On the line's end was a #5 hook and a yarn fly.

"It's a method that has evolved up here over many years," Dave said. "Fly lines work well, also. But the monofilament seems to make a better presentation for steelhead, and catch more fish."

Generally flat -- even, in sections, languid -- the Brule's headwaters some 50 or so river miles upstream from its mouth are flanked by vast spring-fed bogs. Tamarack and spruce are common there, and brook and brown trout take residence, along with beavers, eagles, ospreys and insects so many and varied as to nearly defy definition.

Farther downstream, the Brule gathers itself in swifter currents. This is where Dave, I and my 16-year-old son, Trevor, fished on Wednesday.

Standing now knee-deep in the Brule, Dave made one cast upstream, then another and another.

Size matters to any angler, and the attraction here is the gargantuan nature of Brule steelhead. These fish might weigh 7 pounds or more.

"There we go!"

Dave had hooked up, and a powerful big fish of what seemed like 26 or 27 inches went quickly airborne, drawing his long rod into a deep arch.

Spring steelhead that haven't yet spawned aren't feeding so much when they take a fly. Rather, they intend more likely to dispense with its intrusion into their otherwise very specifically focused lives.

So hooking such a fish in March or April is a fortunate enough occurrence.

Landing them is a bonus.

• • •

Steelhead season opened a week ago Saturday on the Brule, a tradition in the north among Wisconsin and Minnesota river anglers.

Some, like Dave, fish monofilament on fly rods. Others favor fly outfits more conventionally rigged. Still others throw hardware, using spinning rods and reels.

Described often as "the river of presidents," the Brule historically has been fished not only by Midwest anglers but by Calvin Coolidge, Ulysses Grant, Grover Cleveland, Herbert Hoover and Dwight Eisenhower.

Whatever steelheading methods those bigwigs employed -- if they fished steelhead at all, or instead cast only to the Brule's resident brook and brown trout -- it's doubtful they ever were among the throngs who typically descend on the Brule on the season's first day.

This year's opener was reported to be very good, with many anglers hooking up, and many of those actually landing fish.

Curious, that, because success on opening day of steelheading on the Brule depends not so much on the calendar -- as is typical with walleye fishing -- as on a combination of often barely discernible conditions.

Water temperature is one. Steelhead often begin spawning when river water measures in the 40s. Consistent weather counts, too. Like many fish, steelhead can shut down when cold fronts move through.

"The hens, or females, look for the right situation to lay their eggs," Dave said, "and the behavior of the bucks, or males, is tied to when that occurs."

Dave first fished the Brule in 1955, so he has a good idea of where female steelhead in the river prefer to spawn.

When a hen finds such a spot, she prepares a bed for her eggs by rubbing, in spasms, her underside on the stream bottom. A flash of this body-length wiggling, or contorting, is what Dave had seen from the stream bank.

"The bucks will be nearby, ready to fertilize the eggs, and usually, but not always, it's the biggest buck that will win out for that privilege," Dave said. "This is why I refer to steelhead fishing as not so much fishing as hunting. If in spring you can spot a hen preparing her redd, or bed, and cast to that spot, often you won't hook up with the hen, but you might with a nearby buck."

Using this spot-and-stalk method, Trevor had tied in briefly with a nice fish on Wednesday. But the big specimen that had taken his yarn fly was as quickly off the hook as on.

What soon became apparent was that the Brule was far ahead of itself, for so early in the season.

This spring's quick warm-up and fast snowmelt had, it seemed, precipitated an early spawning, and now many steelhead hens were already on their way back toward Lake Superior, a week or even more ahead of schedule.

"I've never seen the Brule, and its steelhead, like this so early," Dave said.

• • •

Toward nightfall we ambled along a streamside footpath to the parking lot where we left our vehicles. By then the half-dozen or so other cars and trucks that had parked there earlier were gone.

It had been a great day.

We had parted a lot of cold spring currents while immersing ourselves in an elaborate webbing of woods and water that soon will blossom from spring to summer.

Also Dave had hooked that big steelhead.

When he did, he and the fish seemed wildly connected, as if by a lightning bolt.

Then Dave's hook slipped from the fish's mouth.

Later, driving west, home to Duluth, Dave doubtless ruminated continually about just that moment, while Trevor and I, heading south, were similarly transfixed.

Dennis Anderson • danderson@startribune.com