Much like the fish they pursue, steelhead anglers are a nomadic breed.

Often departing well before dawn, they drive southbound toward the rock-strewn rapids of the Clearwater, Snake or Grande Ronde rivers. They probe tailouts, scout tributaries and explore deep, rugged canyons.

"For me, it's (about) getting down into that country. Steelhead rivers are just cool, in general," said Pat Way of Orvis Northwest Outfitters in Coeur d'Alene, a fly-fishing guide and veteran steelheader. "It's almost more like hunting than it is fishing sometimes. Really searching and looking. It's almost like prospecting, I guess."

The weather is rarely pleasant - wintertime is steelhead season - and the rivers can be swift and treacherous. Anglers wade through icy water, throwing line through the air. They bounce nymphs, sweep streamer flies.

Some days they'll fish until sundown and leave the riverbank empty-handed. Bad luck happens, especially to fishermen.

But every now and again, when the water is right and the presentation is perfect, they'll reel in a big fish or two.

"I think there's just something about steelhead, the way they've traveled so many thousands of miles in their life," said Mike Beard, another Orvis guide. "Really to enjoy the steelhead, you've got to be able to enjoy the process."

It's been called "the fish of a thousand casts," but diehard fly-casters like Beard and Way embrace the challenge. They love the adventure of steelheading - the cold, snowy weather, the early mornings, even the fickle habits of their elusive quarry.

"You could be doing everything right for 10 days, and not touch a fish. For no fault of your own," Beard said. A good steelheader, he added, "can stand having his feet hurt, and his hands cold, longer than the next guy."

Rial Blaine, manager at Castaway Fly Shop in Coeur d'Alene, enjoys hunting steelhead on the Clearwater River. Mid-winter he tries the Clear Creek run, or a historic hole called Heart of the Monster - an important cultural site of the Nez Perce tribe.

The fish can be difficult to locate, he said.

"You never know if they're there," Blaine said. "Even if you know they're there, they don't necessarily feed like a trout would. (It's) faith. Blind faith. The definition of insanity, I believe."

Patience, though, can yield impressive results. For example, Blaine once caught a 36-inch steelhead that probably weighed 15 or 16 pounds.

And they're fighters.

"The last one I got damn near took the rod out of my hands," Way recalled.

In late February on the Clearwater River drainage, anglers are catching, on average, approximately one steelhead every 10 hours, according to IDFG. Fishing success varies with weather and water conditions; on the wide southern rivers, particularly the Snake, day-to-day water levels can fluctuate by several thousand CFS.

"If you start getting down to five hours a fish, that's pretty good fishing as far as steelheading goes," said IDFG Clearwater Region Fish Manager Joe DuPont.

Greenish-brown with long red streaks down their sides, steelhead are large and powerful fish.

Biologically speaking, there's not much difference between a steelhead and a common rainbow trout. They could be called cousins. But steelhead, to use an Idaho Fish and Game term, are anadromous rainbows - long-distance travelers that spend much of their time in saltwater.

Hatched in the mountain streams of Idaho and Washington, they journey hundreds of miles to the Pacific Ocean. Once in deep water, where food is plentiful, the young steelhead gain weight and muscle.

Then, after one or two years offshore, they heed the call of some strange instinctual voice and swim back upstream, returning to the shallow creeks where their lives began.

From the Columbia to the Snake to the Clearwater, the eastward voyage is long and difficult, full of swift currents and concrete dams that block the route (stair-step fish ladders allow passage). It requires great strength and stamina.

Finally, home at last, the steelhead build rocky nests called redds, lay their eggs and spawn in the springtime.

Most of the Clearwater steelhead are B-Run fish; they spent two years in the Pacific before swimming back to Idaho. B-Runs average around 12 or 13 pounds.

A-Run fish have only lived in saltwater for one year. They tend to weigh much less, about 4-5 pounds. Biologists aren't sure why some fish remain in the ocean longer than others.

"There's a lot of different theories," DuPont said. "There are certainly advantages to being bigger."

Bigger fish, he said, can move bigger rocks when building their redds.

Officials count the steelhead that climb the fish ladders at Lower Granite Dam, downstream from Lewiston on the Snake River. Every run year, roughly 100,000 hatchery-origin fish and 50,000 wild fish negotiate the barrier, according to Fish and Game.

"There's a lot of fish that come by Lewiston," DuPont said. "There is steelhead fishing in our region, the Clearwater Region, from July all the way through April."

Two facilities, the Clearwater Fish Hatchery and the Dworshak National Fish Hatchery, augment the steelhead population. Wild steelhead runs diminished following dam construction along the Columbia-Snake migration route, IDFG officials said. The productive hatcheries now compensate for those losses.

During the cold months of the season, the steelhead that have arrived in Idaho are biding their time until spring. They eat little, but occasionally swipe at lures or flies that wriggle into their territory.

Because steelhead roam big water, and because they're often holding far from shore, many fly-fishermen employ long, two-handed spey rods on the Snake or Clearwater. Spey rods are the heavy artillery of fly-fishing.

"If you get your technique dialed in, you can just rocket that thing across the river," Blaine said.

Once mastered, spey-casting is less tiresome than conventional one-handed fishing, Way said. The long rods allow anglers to fish more water, more efficiently.

"It's really an effective way to fish for (steelhead)," he said.

So far, the 2010-11 season has been unpredictable. The rivers have risen, fallen and risen again. Fishing is hit-or-miss, depending on weather and water and mud and ice.

This week, following rain showers and snowfall, single-digit temperatures are expected in Lewiston.

But the steelhead are still there, waiting for a fly.

"I can count on one hand the number of steelhead I've caught in a T-shirt," Way said. "I guess if it was easy, everyone would do it. As fantastic as it can be, the big thing for me, is you can't have those highs without the lows."