ON THE NORTH SHORE – As I pulled on my waders here Wednesday morning, watching the rushing river far below that I would fish, I thought again how just how wacky spring's biological clock has turned the past ­couple of years.

For the next eight hours, I would chase steelhead with my son, Trevor, 21, who was home from Montana for a couple of weeks, and I was hoping at this late date — May 28 —we could still find a fish or two that would take a yarn fly.

In most years, such an effort wouldn't be worthwhile.

Steelheading is a long-shot game in any event, pursued, oftentimes, in April's bitterly cold rain and sleet, with North Shore stream banks still covered in snow. Ditto those along Wisconsin's Lake Superior shoreline not far away.

But fish, like other wildlife, and also people, respond to weather variations in ways large and small; some so minute as to be barely perceptible.

Steelhead that enter North Shore streams and rivers in spring to spawn, for instance, behave differently than many of those that spawn in Wisconsin rivers that empty into Lake Superior. And not just because Wisconsin rivers are farther south, and warm more quickly.

Spring arrived late on the North Shore this year but nonetheless was in full bloom on Wednesday. Streams were warming quickly, and dropping, pushing steelhead back into Lake Superior after ­entering the rivers perhaps weeks ago to spawn. The hope was for one more good day of fishing; the result was a clear indication the steelhead season was over.

Example:

Wisconsin's Brule River (Minnesota's North Shore also has a Brule River, north of Grand Marais) receives its biggest runs of steelhead in fall; fish that overwinter in the river before spawning in spring and slipping back downstream, sometimes tail-first, to Lake Superior.

But the same fish that enter Minnesota's North Shore streams do so in spring, before returning again days or weeks later to Lake Superior. These fish have little choice: Unlike watersheds drained by the Wisconsin rivers, those emptied by Minnesota ­rivers and streams into Lake Superior are fairly small, and once they've deflated the region's snowmelt, and spring's heavy rains, their ­levels drop precipitously. And their temperatures rise.

Neither of which is good for steelhead, which prefer cold water, and also favor rivers pockmarked with deep pools capable of providing protective cover from various predators, including eagles and ospreys.

Many anglers consider steelhead (migratory rainbow trout) among the world's strongest and most beautiful freshwater ­fin-bearing critters, and they start looking for these fish along the North Shore when stream temperatures nudge 40 degrees. It's then that mature (3- or 4-year-old, or older) steelhead begin to filter into the region's rock-strewn rivers.

For anglers, the trick is to locate spots where the fish "hold,'' while running upstream. Springs that unfold fairly slowly, with river temperatures rising only gradually, and water levels remaining fairly high, usually provide the most consistent fishing, and the greatest number of days steelhead can be found in North Shore ­rivers.

Consider now this spring, which arrived late, especially in northern Minnesota, and, when temperatures finally did rise, produced peaks of incredibly raucous river flows north to south, along the North Shore.

Steelhead can fight their way up raging rivers. But anglers can't fish these waters very well, efficiently or safely.

So this spring, steelheading got a late start. Which is the bad news. The good news is steelhead have been around in some North Shore streams in reasonable numbers much later into May than is ­usually the case.

Proving the point, Trevor, along with Dave Zentner and Mark Kilen of Duluth, on Tuesday hooked eight steelhead. Four were landed, an admirable percentage.

Now it was Wednesday morning, and Trevor and I would try our luck. But as we hiked upstream a mile or so along one of our favorite rivers, we worried that fast-changing conditions might prove our undoing. The water level had dropped from the day before, and the river temperature was higher by about 3 degrees, hovering near 60.

Still, in a pretty run of water bracketed canyon-like by steep banks, we waded into swift water.

"Let's try it here,'' Trevor said.

And we started casting.

Season's end

Five hours later, having fished upriver to a barrier falls and failing to hook up, we knew any steelhead we would catch on this day would be well-earned.

North Shore steelheading, it seemed, was ending for the season before our very eyes. Or had ended overnight.

The day before, at these same falls, Trevor, Dave and Mark had seen a handful or more of steelhead jumping or porpoising in the pool below the falls in vain attempts to swim farther upstream.

Wednesday in that pool, only one fish showed itself.

"We're going to have to work our way downstream to the lake, to see if we can find any fish holding on their way out,'' I said.

So it was beneath a cloudless sky, with trees budding and ravens yapping overhead, that we bounced egg-pattern yarn flies through likely-looking lies, or holding spots. This wasn't fly casting of the iconic variety, with long floating lines looping overhead, and tapered leaders and flashy streamers trailing.

Instead, our fly reels were spooled with monofilament, and our leaders weighted with splitshot. Thus rigged, we "walked'' our flies downstream, bouncing the weights along the river bottom, hoping our flies would entice pick-ups.

After so many strikeless casts, I had been lulled into complacency, and was slow to set the hook when I felt a telltale tug.

It was a steelhead, and the fish's broad side flashed in the bright water.

As quickly, my line went limp.

As darkness blanketed Hwy. 61, we headed for home, tired. I had driven up that morning, a four-hour run, and Trevor had made a similar jaunt the morning before.

Between us, for two days of fishing, we landed one steelhead — a dandy buck Trevor took the day before.

"A great time,'' I said. "But I think the season is over.''

Dennis Anderson danderson@startribune.com