Recruitment of Rainbow Trout from Tributaries to the Kootenai River, Idaho

Rainbow trout provide the most important remaining sport-fishery in the Kootenai River, Idaho, but densities are low. Low juvenile recruitment is hypothesized as one reason for these low densities. We addressed this hypothesis by quantifying rainbow trout recruitment from tributaries in Idaho. A rotary screw trap, drift nets, and snorkeling were used from 1997-2002 to estimate age-0 rainbow trout production and the number of juvenile out-migrants. The Deep Creek drainage was the most important nursery area contributing an average of about 39,000 recruits each year. Most (.97%) spring out-migrants from the Deep Creek drainage were age-1 and 2. The average annual production of age-0 rainbow trout in Kootenai River tributaries upstream of Deep Creek was 9,985. Boulder Creek is the largest source of recruits in this reach of river, averaging about 4,000 age-0 rainbow trout out-migrants each year. Differences in life history and spawning locations require different management approaches for the Deep Creek drainage versus Kootenai River tributaries farther upstream. Management of the Deep Creek drainage could incorporate land management practices that help conserve and enhance spawning and rearing habitat. Management options for increasing recruitment from tributaries upstream of Deep Creek could include enhancing, or increasing access to spawning gravels, more conservative fishing regulations to increase adult numbers, and strategies to improve primary productivity.