Hatchery supplementation has been developed to conserve salmonid populations and provide fisheries. We evaluated supplemented and reference Chinook salmon (Oncorhynchus tshawytscha) populations prior to, during, and after supplementation ceased for 22 years in two major drainages in Idaho, USA. Basin-level analyses showed supplementation increased abundance at some life stages, but effects did not persist into the postsupplementation phase and had no apparent influence on productivity. Natural-origin juvenile abundance increased during supplementation but results for adults were ambiguous. After supplementation ceased, abundance and productivity in supplemented and reference populations returned to their presupplementation relationships. Intensive analyses of supplemented populations with weirs showed abundance increased at some life stages with the addition of female spawners. However, the rate of increase varied with female origin (natural > supplementation ≥ nontreatment hatchery), and effects diminished through the life cycle. Based on these findings, we provide guidance for conservation programs. Supplementation alone is not a panacea because it does not correct limiting factors, which must be addressed to achieve population levels capable of sustaining ecological function and harvest.

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Setline and angling techniques were used to sample 332 sturgeon from the river between Kootenai Falls and Kootenay Lake during 1989 and 1990. Sturgeon were found in Montana within 4 km of Kootenai Falls and downstream from Bonners Ferry, Idaho to Kootenay Lake, British Columbia. Our data indicate there is a complete lack of recruitment of juveniles into the population. The youngest fish sampled was of the 1977 year class, and the population is estimated at 880 individuals with 95% confidence intervals of 638 to 1,211. Culture of one pair of sturgeon in 1990 was of limited success. Less than 5% of eggs hatched with 50% initial mortality of fry. The contribution of contaminants found in eggs (aluminum, copper, toward this poor survival is unknown. zinc, lead, and organochlorides) Handling problems with the eggs at the time of spawning complicated our results. An ongoing sonic telemetry study has revealed definite long distance movements. Sturgeon regularly move across the British Columbia-Idaho border and seek out deep holes or migrate to Kootenay Lake during late fall. Seasonal differences in use of depth and velocity parameters were found between sexes and among seasons. No relationships were found between sturgeon movement and month, water temperature, flow, and flow change. However, multiple regression analysis indicated that up to 30% of the variance in individual sturgeon movement was explained by the combination of the four variables.