Chasing steelhead in the Boise River has become a fall tradition for many Treasure Valley anglers. Most Novembers, Idaho Fish and Game staff, in cooperation with Idaho Power Company, move up to 1,000 adult steelhead from the Hells Canyon Dam fish trap to five release locations on the lower Boise River. Anglers, often times numbering in the hundreds, patiently await transport trucks. The reward for these anglers who patiently brave the cold and the crowds? An opportunity to catch one of the most prized freshwater sport fish in North America in the heart of Idaho’s biggest city.
The program has a long history. The first of these transplants occurred over 35 years ago, in 1983. Based on fish availability, the transfers continued intermittently through the mid-1990s. Starting in 1995, transfers continued uninterrupted for 24 years until insufficient returns lead to no stocking of the Boise River in 2019. However, that hiatus was short-lived as fish were once again available in 2020.
What determines if fish are available for the lower Boise River?
The primary purpose of trapping adult steelhead at the Hells Canyon Dam is to collect broodstock adults to provide enough eggs for the Niagara Springs Fish Hatchery to produce 800,000 smolts to be released into the Snake River below Hells Canyon Dam and into the Little Salmon River. Adults trapped in excess to those needed for broodstock are distributed evenly between the Nez Perce Tribe, Oregon Department of Fish and Wildlife and Idaho Fish and Game. Idaho uses its portion of these surplus fish to create a fishery in the lower Boise River. The year-specific number available depends on the overall surplus. In a year like 2019 when only enough adults are trapped for broodstock needs, no surplus fish become available for the states and tribes to distribute.
How many of these fish are actually caught by anglers?
The primary purpose of moving these hatchery fish to the lower Boise River is to create additional steelhead opportunity for Idaho anglers. But how many are actually caught is a question Fish and Game has tried to previously answer numerous times using various methods. But traditional methods such as angler creel or phone surveys are either costly or can potentially contain a high degree of error. However, a recent statewide steelhead tagging study conducted by the University of Idaho provided a unique opportunity (University of Idaho study). That study is utilizing Idaho Fish and Game’s well-established Tag! You’re It! fish tagging program to study steelhead encounter rates in the Clearwater and Salmon rivers. Through the use of reward tags, it has generated a key piece of information: the rate at which anglers report non-reward tagged hatchery steelhead in Idaho.
Armed with that key piece of information, fisheries staff tagged 20 percent of the steelhead released into the Boise River in 2020 and waited for anglers to report tagged fish that they had caught. In the roughly two months following the stocking, anglers harvested just under 80 percent of the fish. This means that by the end of January, anglers harvested an estimated 316 of the 400 fish that were put in the river in November. The results of this study confirmed that a high proportion of hatchery steelhead that are transplanted to the Boise River are harvested by steelhead anglers, and that the program is achieving its goal. Fish and Game hopes to continue this tagging work in future years to see if the high harvest rate continues, especially in years where a higher number of fish are released into this fishery.
Idaho Fish and Game thanks all of the anglers who reported tagged fish as part of this work.