Stephen J. Owens and Phillip W. Bettoli, Tennessee Cooperative Fishery Research Unit, Tennessee Technological University, Box 5114, Cookeville, TN 38505

Abstract. The South Fork of the Holston River, Tennessee, has been managed by the Tennessee Wildlife Resources Agency as a tailwater trout fishery since 1952, but the growth of salmonids in that system has not been studied. Four cohorts of about 6,000 rainbow trout Oncorhyncus mykiss and 16,000 brown trout Salmo trutta were microtagged and stocked at different times in 1997. Monthly electrofishing samples were collected between March and November 1997; each trout was measured, weighed, and checked for the presence of a microtag. Growth rates for the different cohorts of microtagged trout were calculated and compared. Mean growth of the four rainbow trout cohorts averaged 13 - 22 mm/month and 25-51 g/month, and growth rates varied among cohorts (P 0.05). Hatchery-reared brown trout grew 11 mm/month and 20 g/month; wild brown trout grew 11 mm/month and 18 g/month. Hatchery brown trout grew at similar rates to resident wild brown trout. Hatchery trout grew faster in this system than trout studied in other Tennessee tailwaters. Rainbow trout stocked later in the season showed a trend for faster growth in weight than earlier stocked trout. Except for rainbow trout stocked in July, the relative weight of stocked fish declined consistently over time.