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r RESULTS AND DISCUSSION Life history of the rainbow trout has been studied thoroughly since they were first stocked in the reservoir in 1963. The age and growth of rainbow trout between 1963 and 1970 was summarized by Varley et al. (1971a). Age and growth of rainbow trout for the period 1975 through 1979 was described by Schmidt et al. (1980b). Differences in growth rates between these two reports are explained by the changes in size of stocked rainbow trout. Stocking size was increased from an average of 3 inches to 5 inches in total length beginning in 1973. The smaller rainbow trout planted from 1963 to 1972 grew faster than the plants of larger fish. Therefore, at the end of the first year, the rainbow trout planted at 3 inches were only slightly smaller than trout planted at the larger size. Table 30 summarizes the back-calculated total lengths of Flaming Gorge rainbow trout captured during 1975-1979, by year class for each of the three areas of the reservoir. First year growth of Flaming Gorge rainbow trout was 5.4 inches, 6.7 inches, and 6.2 inches respectively for the Canyon, Open Hills, and Inflow Areas. This is 1.9, 1.3 and 2.0 inches slower growth, respec- tively, than calculated during the period 1963 through 1970. Age-growth and fishing effort information was used to analyze the exploita- tion of the rainbow fishery by Wiley et al. (1977). Simply stated, the results suggested by Wiley et al. (1977) for the period 1970 through 1975, did not change during the period described by Schmidt et al. (1980b). Rainbow trout grew well in their first year of life in the reservoir and age group I fish dominated the harvest. Slower growth occurs between ages I and IV and faster growth occurs after age IV (Figure 8). The age composition of creeled rainbow trout during the period 1975 through 1979 is presented in Table 31. As in the past, over 50 percent of the harvest came from age group I and only 1 percent of the rainbow harvested were age IV or older. The information collected during 1975 through 1979 for rainbow trout shows that rainbow trout have a relatively low survival rate, high rates of natural mortality, yearly variations in the rate of fishing mortality and age group I fish dominate the harvest. Reasons for the high rates of annual mortality are predation by lake and brown trout, competition for zooplankton, inability of domestic strains of rainbow trout to use the forage base of the reservoir and poor survival during the winter. Condition factors (C) computed for Flaming Gorge rainbow trout harvested from three areas of the reservoir are found in Table 32. The Inflow Area had consistently higher condition factors than either the Open Hills or Canyon Areas. Fish from the Canyon had the lowest condition factor in the reservoir. Figure 9 depicts the mean condition factor (C) of rainbow trout by age group from the three areas of the reservoir from 1975 through 1979. The increase in condition factors after age group IV in the Canyon is related to the faster growth rate achieved by the few rainbow which are able to switch from zooplank- ton to a fish diet. These rainbow (ages IV through VIII) may have been the rem- nants of the 1969, 1970, and 1971 plants of Kamloops rainbow trout. Age-growth determinations and. condition factors for rainbow trout were not studied after 1979, because of the findings from 1975 through 1979. Very little change had occurred between the studies on rainbow trout done by Varley et al. (1971a), Wiley et al. (1977), and Schmidt et al. (1980b). Age-growth and condition factors for brown trout in Flaming Gorge were described by Varley et al. (1970), Varley et a1. (1971b), Starostka et al. -56-