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Big Horn River fish prospering

Randy LaBeff with a rainbow from his 30-fish day on Montana’s Big Horn River.
Randy LaBeff with a rainbow from his 30-fish day on Montana’s Big Horn River.

Year’s ago, Outdoor Life magazine headlined Montana’s Big Horn River as the best trout stream in American. Today it appears to be at least that good.

Abundant water years have allowed the brown trout population to soar on the popular Bighorn of south-central Montana, making last year’s roughly the fourth-highest trout count since 1986.

“The 2011 year class is really strong coming up,” said Mike Ruggles, Fish, Wildlife and Parks fisheries biologist.

As fish populations have climbed, so has the number of anglers venturing to the world-renowned stream popular with fly fishermen. The number of angler days was estimated at 130,000 in 2011.

“Last year was just exceptional as far as how productive the fishing was,” said Hale Harris, owner of the Bighorn Trout Shop in Fort Smith.

Bookings for guided trips and rooms in the area about 90 miles southeast of Billings are on par or ahead of normal for the coming fishing season, he added. The river fuels a local fishing industry that generates an estimated $50 million a year.

Based on surveys conducted last year, the upper river held about 8,000 fish per mile. That figure includes about 2,900 brown trout 9 inches or larger per mile and about 1,300 rainbow trout 9 inches and larger per mile. Adding in smaller fish brings the total up to 8,000.

“So there are a lot of little guys out there,” said Ken Frazer, FWP regional fisheries manager, with quite a few 15- to 19-inch brown trout in the mix.

Farther down the river, near Mallards Rest fishing access site, FWP counted 1,950 brown trout 9 inches and larger per mile and only 134 rainbow trout 9 inches and larger per mile. Including smaller fish, the total count was 2,600 fish per mile.

“A lot of times we don’t see many rainbows in that lower section,” Frazer said.

The strong trout numbers are the result of a big water year in 2011 that not only filled Bighorn Reservoir, which feeds the river, but also flushed the waterway’s gravel free of silt, creating excellent spawning conditions. More water also creates more habitat, flooding side channels that offer hiding spots for young fish to avoid predatory larger trout.

Unfortunately, the past summer, fall and winter have been fairly dry, meaning the future of water flows in the Bighorn River are subject to how much snow and rain fall this spring. FWP likes to see the river running at 2,500 cubic feet per second, with a minimum of 1,750 cfs. The Bureau of Reclamation controls the dam releases, trying to balance the needs of reservoir users, river users, irrigators and power generation.

“At 2,000 cfs we start losing most of the side channels, so there’s less habitat,” Ruggles said.

In 2011’s record runoff, the snow came in April and lasted into June because of a cold spring.

Bighorn Reservoir was roughly 90 percent full last week. But runoff into the reservoir is predicted to hit only 63 percent of average this spring and inflows were 78 percent of average in February and had dipped to 1,750 cfs last week after spiking in mid-March.

“We’re hoping we get moisture here in midspring,” Harris said. “It’s helpful for the hatches if we get a flushing flow.”

He added that in the last couple of years, the insect hatches have been good after some bugs nearly disappeared in previous drought years.