Reproductive Cycle and Associated Changes in Energy Content of Body Tissues in Rainbow Trout from the South Fork Holston River, Virginia

The spawning period and caloric density of body tissues during gonadal recrudescence were studied in a naturalized population of rainbow trout (Salmo gairdneri) from September 1979 to August 1980. As judged by gonosomatic indices and the percentage of spent females in semimonthly samples, the fish spawned from mid-February to early April, when water temperature and stream flow were both increasing. Decreases in calorific equivalents (cal mg-1 dry weight) of selected tissues during gonadal maturation in fall and winter were greatest in fat reserves along the alimentary tract.