Light hatches of caddis and mayflies shortly after daylight marked the beginning of my fly-fishing trip on the Boise River. But they were no match for the rubber hatch that materialized at about 10 a.m. that day. Inner tubes and small rafts appeared on the river and grew heavier by the minute until they dominated the summer scene.

"That's the way the river gets almost every day of the summer," pointed out Boise flyfisherman John Wolter. "With the BSU (Boise State University) campus right next door -- something like 18,000 students -- the river plays a major role in summertime fun in Boise."

For the angling crowd, fun under the summer sun on the Boise River includes tapping local populations of rainbow and brown trout along the Boise River Greenbelt, the city-owned parkland that stretches along more than 12 miles of the river.

"It's a very viable fishery for being situated in a city," says Wolter, who owns Anglers, one of Boise's premier fly shops. "The Boise not only presents good opportunity to catch a lot of fish, but for the guys who get off the beaten path, the river also offers a lot for anglers who want to catch wild rainbow and brown trout."

ALONG THE BEATEN PATH
The Greenbelt is open to anglers as well as cyclists, hikers, skaters and runners, via 25 miles of paved and graveled paths. Barber Park bounds the Greenbelt at the upstream end. Downstream, its recognized boundary is the Glenwood Road bridge.

Wolter and I began our day wading a long stretch of the river adjacent to Ann Morrison Park at Americana Boulevard. Here, the river bottom is generally flat and open -- with a wide freestone bottom and riprap banks, with just a few small willow trees. It's a good starting place early in the morning, Wolter pointed out. Later in the day, floaters and tubers use the park's flat shoreline as a take-out point just upstream from a diversion dam that ends a two-mile float from the usual put-in point at Barber Park.

The bridge near Ann Morrison Park at Americana Boulevard is also one of several locations where the Idaho Department of Fish and Game stocks thousands of rainbows each month.

Here and there, a rise marked the feeding locations of some of those trout. Wolter quickly armed his leader with a size 18 Light Cahill dry fly. Because distance can be a factor in reaching these fish, an 8 1/2- to 9-foot, 4- or 5-weight fly rod/reel combo is your ideal setup. A rainbow in the 10-inch class rewarded Wolter's fast cast in the vicinity of the rise.

I chose a size 18 Elk Hair Caddis. It drew a few strikes that I missed. Then I set the hook solidly on a trout that jumped twice before I played it to hand. Admiring my 12-inch catch, I discovered orange slash marks under its chin. Wolter suggested the fish was a cuttbow -- a cross between a rainbow and a cutthroat. But its presence here left him a little bewildered.

"For several years now, the stockings the state's been making have been triploid rainbows," he explained. "Those are sterile fish, so crossbreeding is a very rare occurrence."

Brian Malaise, assistant hatchery manager at the IDFG's Nampa Fish Hatchery, said the incidence of crossbreeding between rainbows and cutthroats in the Boise River is nearly impossible. "In fact, the chance of a cuttbow in the Boise River is slim to none. According to our fisheries biologists, the native trout of the Boise River is the rainbow," he said.