Summer habitat use by rainbow trout and brown trout in Jocassee Reservoir

Temperature, dissolved oxygen, and depth preferences of Jocassee Reservoir rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta implanted with temperature-sensing radio transmitters were determined during July, August, and September 1994-1998. Specific knowledge of these preferences was needed to verify habitat criteria designed to assist in the management of water quality in this reservoir for trout survival in late summer and early fall. Rainbow trout exhibited temperature, dissolved oxygen, and depth preferences in the ranges 8.3-13.4 degreesC, 2.9-8.7 mg/L, and 30.0-52.0 m, respectively, while brown trout exhibited preferences in the ranges 7.5-21.9 degreesC, 4.2-10.0 mg/L, and 14.0-54.0 m, respectively. Even though rainbow trout selected cooler water temperatures and greater depths than brown trout. both species generally exhibited preferences for water 20 degreesC or cooler and containing 5.0 mg/L or more of dissolved oxygen. Maintenance of these criteria in Jocassee Reservoir should ensure adequate habitat for the summer and early fall survival of rainbow and brown trout.