Includes bibliographical references.

Estimated kokanee (Oncorhynchus nerka) abundance in Lake Pend Oreille was 4.3 million during September 1986. This estimate was similar to 1985 and indicates continued suppression of the kokanee population since initial decline in the late 1960s. Atypically high survival of wild fry resulted in similar fry recruitment in 1986 as 1985, whereas hatchery-reared fry contributed only 8% to total fry recruitment as a result of low post-release survival (3%). Fry released into the Clark Fork River from Cabinet Gorge Hatchery had very low survival during emigration to Lake Pend Oreille, resulting from poor flow conditions and potentially high predation. Fry survival during emigration was twice as high during nighttime flows of 16,000 cfs than 7,800 cfs. Emigration also was faster during higher flows. Several marks were tested to differentially mark fry release groups to help determine impacts of flow and other factors on fry survival. Survival of fry marked with tetracycline and fluorescent dye was high (>99%) during the 10-week study. In contrast, survival of fry marked with fluorescent grit marks ranged from 5 to 93%, depending on application pressure and distance from the fry. Retention was high (>96%) for tetracycline and grit marks during the study, whereas dye marks were discernible (100%) for only one week. Total egg take in 1986 was 9.1 million, with 7.3 million collected at Sullivan Springs. This low take represented 32% of the eggs necessary to fill Cabinet Gorge Hatchery and reflected the lowest fry-to-adult return rate to Sullivan Springs since initiation of enhancement efforts in the mid-1970s. Low escapement to Sullivan Springs may have been the result of a major freshet in Granite Creek that flushed spawners out of the system during the peak of the run and/or straying.

DE-AI79-85BP22493 85-339