Mark L. Nemeth and Phillip W. Bettoli, Tennessee Cooperative Fishery Research Unit, Box 5114 Tennessee Technological University, Cookeville, TN 38505

Francis C. Fiss, Tennessee Wildlife Resources Agency, PO Box 40747, Nashville, TN 37204

The South Fork of the Holston River in east Tennessee last year received over 900 hours per hectare of fishing pressure. The 20-km tailrace is stocked annually with about 72,000 catchable rainbow trout Oncorhynchus mykiss, 11,000 brown trout Salmo trutta, and some natural reproduction by both species occurs. To obtain more information about the survival of trout in this tailrace, four microtagged cohorts of rainbow trout (>5800) and one cohort of brown trout (16,670) were stocked between March and September 1997. Survival was investigated by electrofishing each month and conducting a creel survey. Rainbow trout stocked in early summer survived better than trout stocked earlier in the year. Brown trout survived better than rainbow trout stocked at the same time. A change-in-ratio mark-recapture technique estimated the combined population of rainbow trout and brown trout at 56,493 fish in the first 16 km of the tailrace; total trout biomass was estimated to be 214 kg/hectare. The number of wild brown trout less than 270 mm total length was 18,522.