The local Hemingway chapter of Trout Unlimited relocated 1,055 trout upstream into the Big Wood River last Tuesday after discovering a nearly dried-up section of the river south of Bellevue.
The rescue operation—led by chapter President and Hailey resident Ed Northen—used a trailer with a water tank to transport trout to a section of the Big Wood River along Broadford Road.
Since 2008, Northen and fellow Trout Unlimited volunteers have rescued tens of thousands of rainbow and brown trout trapped in canals below the Glendale diversion. The Hailey-based chapter has rescued about 60,000 fish over the past 12 years, he said, averaging about 5,000 per year.
“That’s a conservative estimate,” he said. “And we’re just rescuing a small portion of the fish that are trapped.”
The water level at the stretch of river where Northen and seven other volunteers stationed themselves last week had dipped dangerously low due to recent dewatering activity for irrigation, he said. Most of the fish they saved were wild rainbow trout, along with a few dace and Wood River sculpin.
“We rescued a mix of juvenile and mature trout, some over 18 inches. Within two hours of arrival, literally all water had evaporated from this area,” he said.
Northen said in years with higher river flows, the Big Wood Canal Co. is able to divert more water into its system of canals. But when it becomes evident that there’s not enough water for those with senior water rights, irrigation systems are shut off.
“Because diversion [points] along the river don’t have fish screens on them, the fish get entrained down into the canals,” he said. Low water levels, warming water temperatures and plant growth then lead to a depletion of oxygen.
When Northen receives word from a rancher or water manager about an evaporating canal or section of the Big Wood River, the Trout Unlimited chapter quickly mobilizes. A 300-gallon water tank on a trailer—complete with its own oxygenation system, bubbler and flow meter—is retrieved from a storage unit, filled and driven to the rescue site.
“We use a large net to gather fish, place them in five-gallon buckets and get them into oxygenated water in the tank very quickly. That allows us to rescue a lot of fish at a time,” Northen explained. “Then, we drive north to the lower Broadford Road bridge, open the [tank] gate and let the fish out into the river. We don’t want them swimming back into the canals.”
Due to limited water availability this year, Northen anticipates a shorter irrigation season with early canal closures. He also expects the Idaho Department of Fish and Game to initiate a trout salvage for the Big Wood River south of Magic Reservoir, meaning people would be able to net as many ill-fated fish as they want.
“In high-water seasons, trout survival is better because they have the option to migrate to deeper, cooler pools. But in low-water seasons when the water is shut off, they can’t access those areas,” he said.
According to U.S. Geological Survey data, the Big Wood River has experienced record low flows this month—a factor that may be accelerating evaporation. From June 8-17, the Lions Park gauge site in Hailey recorded an average flow rate of about 537 cubic feet per second, well below the average for that time period of 1,585 cfs. Farther north in Ketchum, the Big Wood River hit its lowest-ever recorded flows for those 10 days; the previous low-flow records for June 8-17 were set in 1966 and 2013, USGS data show.
Northen, an avid fly fisherman, said installing fish screens at diversion points or shutting off water more gradually could dramatically boost fish survival—but those changes are costly to implement.
“The Big Wood River is a very resilient fishery. It’s amazing how well trout have survived, given the circumstances,” he said. “But if we could work with water users on reducing irrigation demand and collaborate more closely with the [Big Wood] canal company, we could see a world-class fishery.”
A subsequent Trout Unlimited rescue project near Gannet Road is planned for this week, Northen said, and further relocation efforts will continue until fall.
“It’s troubling to see trout end up in hot water and die, especially when you have the opportunity to relocate them,” he said. “Dewatering, unfortunately, has occurred for decades.”
In an interview last week, Fish and Game spokesman Terry Thompson stressed that it’s illegal to transport live fish without a permit due to the possibility of spreading disease across water bodies. That goes for even well-intentioned efforts to relocate trapped fish after water is diverted or turned off, he said, and Trout Unlimited is able to carry out its projects only because it has the necessary permitting.
Anyone interested in volunteering with Trout Unlimited on future trout-rescue projects can contact the Hemingway chapter at email@example.com.