THE EFFECT OF DIET PROTEIN LEVEL, FEEDING LEVEL AND REARING WATER TEMPERATURE ON THE GROWTH AND REPRODUCTIVE PERFORMANCE OF RAINBOW TROUT BROODSTOCK (WASHINGTON)

Two separate feeding trials were conducted using University of Washington rainbow trout broodstock to determine the effect of dietary protein level, ration size and water temperature during the period of gonad development on their pre-spawning growth and reproductive performance. During the eight months prior to spawning four isocaloric diets with 27, 37, 47 or 56% protein were fed to separate groups of the 1973 brood and four groups of the 1974 brood were reared under the cross-classified design of two water temperature profiles, cool and warm; and two ration sizes, repletion and half-repletion (as a % of body weight per day).;The dietary protein requirement for maximum growth was between 37 and 47% of a diet containing 3.8 kcal/g metabolizable energy (dry matter basis). Caloric utilization, food conversion and protein efficiency ratio decreased with increasing levels of dietary protein. Dietary protein level did not affect prespawning mortality, spawning success or the duration of spawning. Dietary protein level did not have a significant effect on the absolute or relative number of eggs spawned, relative egg size or embryo survival.;Maximum growth was achieved by feeding repletion rations under warm water conditions. Food and protein utilization for growth was optimum with repletion rations in warm water or half-repletion rations in cool water. Feeding repletion rations in warm water increased pre-spawning mortality. Water temperature or feeding level did not affect spawning success, but feeding half-repletion rations increased the duration of spawning and warm water delayed the time of spawning. Relative fecundity was increased by feeding half-repletion rations in warm water. Relative egg size was increased by feeding half-repletion rations in cool water. Warm water and feeding repletion rations had deleterious effects on embryo survival due to their effects on egg size. Ration size also had an independent effect on embryo survival.;Length, weight, condition factor, food conversion, caloric utilization, protein efficiency ratio, pre-spawning mortality, the time and duration of spawning, egg production, egg size and embryo survival were measured to determine the effects of dietary protein level, feeding level and water temperature on pre-spawning growth, food efficiency and reproductive performance.