"I know a guide that has a list of clients with their phone numbers," said Rhett Bain of Reel Deal Fishing Adventures. "As soon as this hatch starts going, he'll call them and they'll hop on a plane and get there. That's how incredible it is."

Hatch conditions

If you hit the salmonfly hatch just right this season, be sure you have plenty of film in the fly vest for shots of big rainbows.

"In most years, that window (of opportunity) is June 10th through the 25th, with the prime time being the 15th to the 20th of June," said John Flick of Duranglers Fly Shop in Durango, Colo. "When conditions are dry, the hatch is typically earlier and when conditions are wet, it's typically later."

With Colorado's relatively stable and warm late spring weather, Flick expects a solid, but quick hatch on rivers like the Rio Grande and the Gunnison.

Farther north, Bain expects the hatch to really begin to boil within the next two weeks - depending on the weather. Last week, a late May snowstorm assaulted the region around his Jackson Hole, Wyo. home.

Matching the hatch

Matching the hatch of these two and a half inch long Pteronarcys californica stoneflies usually doesn't require an angler to fill a fly box with dozens of imitations, thanks in part to the insect's large size.

"It's a big honker," laughed Bain. "It is by far the most protein filled hatch out of the whole season. Some of these fish can grow two-inches during this hatch.

Add in the insect's simple coloration and fly selection is usually simple.

"It has a salmon-like orange belly on the adult," Flick said. "You can even see a bit of that on the nymphs when they're almost to emergence. But for the most part, the nymphs are dark brown to black."

Here are a few fly box suggestions for the salmonfly hatch:

• Nymphs — #6 sized Kaufmann's stones in brown and black colors; Golden stones; Ted's Golden stones; Bead-head stonefly nymphs in yellow, brown, or black; Bitch Creek nymphs; Brook's stone nymphs; Willow nymphs; 20-Inchers; Big Princes; Half-black nymphs; Girdle bugs; and black Wooly Buggers.
  While #6 nymphs are usually the best size, Roaring Fork Anglers guide and map-maker/outdoor writer Michael D. Shook of Carbondale, Colo. advises anglers to carry some smaller salmonfly nymph imitations since several generations of the big stoneflies will be in water like the Colorado River at the same time.
  
• Dry flies — #4-6 Improved Sofa Pillows; standard Sofa Pillows; Stimulators; Rogue stones; Henry's Fork salmonfly; Jugheads; Picket-pins; Marcellas; Troth's Salmon; Madame X; Turk's Tarantula; and Chernobyl ants.
  

Tackle selection

When anglers catch the salmonfly hatch just right, rainbow, brown and cutthroat trout can be caught on virtually every cast.

These are big bugs on typically big, brawling western freestone rivers. Grab a nine-foot five or six-weight fly rod and leave the fine, long leaders and tippets at home.

"I'm fishing 2X," said Flick. "If they're going to eat the big bug, they could care less about the leader. I use a seven and a half-foot leader and I fish a lot of eight-pound Maxima. It's stiff and helps turn the big bugs over and it's more abrasion proof.

"A lot of places where you find the salmonfly, it's rocky — that's how stoneflies get their name. There is lots of abrasion and a 4X leader doesn't stand a chance."

Techniques One key to properly fishing this hatch is to remember that the salmonfly doesn't hatch from the water like a mayfly or caddis fly. Rather, they crawl from the water as nymphs and ditch their exoskeleton on rocks near the river. Then they'll crawl into nearby trees for mating prior to clumsily testing their wings or getting blown into the river.

Armed with this basic knowledge of the salmonfly's life cycle, anglers should key their search for feeding trout closer to the bank rather than farther away from it.

"These flies are flying around through the air and falling from the willows and tamarisks to the water, so anglers should really concentrate on the water right near the bank," Shook said.

Shook believes that overcast and cloudy days can provide the best dry fly action since trout don't like to look into the sun. He also discourages the use of a dropper rig on the Colorado River, suggesting that a single dry fly is best.

Flick takes a different approach from Shook after experiencing some superb salmonfly surface activity on sunny, mild days. He also advises anglers to dead drift their big dry flies with perhaps an occasional twitch or flutter.

Regardless of the sky conditions, presentation is seldom an issue according to Bain. In fact, slapping the fly onto the water can actually simulate the noisy landings of the clumsy salmonfly.

"Presentation is not nearly as critical as in matching the hatch later during a BWO hatch with a #22 dry fly on a 7X leader," Bain laughed. "This is a much more forgiving hatch."

Finally, Shook suggests that it pays for an angler to stay ahead of this hatch when possible.