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Considering intra-specific competition for food there is suggested a possible single area of significant intra-dependency: both rainbow and brown trout ranging in size from 201 mm through 400 mm included comparable amounts of zooplankton in their diet. Whether or not the zooplankton were obtained from the same ecological niche is, how- ever, not known. Results showed differences in food items to be insignificant between species when all sizes were combined. There were, however, significant differences between species in some size groupings (Table 2). Rainbow consumed zooplankton in decreasing amounts up to 501 mm (19.7 inches) (Figure 2). Rainbow trout may include more insects, aquatic and terrestrial, in their diet than do brown trout but differences in mean volumetric concentrations were not significant at the 95 and 99 percent level of significance (Tables 1 and 2). Brown trout between 251 and 450 mm (9.9 to 17.7 inches) used significantly more forage fish than did rainbow of the same size. Utah chub (Gila atraria) were the most numerous of the identifiable forage fishes, Redside shinners (Richardsonius balteatus), sculpin (Cottus bair- di) and trout were also identified. The mean percent stomach volume of fish increased with the size of trout captured (Figure 3). Borgeson (1966) suggests that trout begin to use forage fish in substantial amounts in the size range 305 to 406 mm (12 to 16 inches). Arbitrarily assuming that 15.0 percent by volume constitutes a significant dietary contribution, brown trout over 251 mm (8.9 inches) and rainbow over 451 mm (17.8 inches) use substantial amounts of fish. Brown trout consumed more forage fish than did rainbow. McAfee (1966) and Swift (1970) reported similar trends in California waters. Utah chub ranging in length from 102 to 152 mm (4 to 6 inches) were most common in the stomachs. Mullan et al. (1968) suggested that size of the forage species is an important consideration. According to Eiserman et al. (1967) rainbow utilized fish in their diet in decreasing amounts down reservoir. We found this trend to continue through 1969, (Table 3). Gillnetting information suggested that forage fish were more abundant in the inflow area and decreased down-reservoir. This indicates that the use of forage fish may be related to their abundance. Cannibalism in rainbow and brown trout was apparent. Information obtained throughout the project indicated the bulk of cannibalism to be linked with the stocking of fingerling trout. During 1970, nets were set following a plant of 65,000 fingerling (76 mm) rainbow trout. Two of the netted trout over 305 mm (12.0 inches) contained identifiable trout remains. No fish less than 305 mm contained fingerling remains. Field observations of the stomach contents of angler-caught-fish indicated that cannibalism probably occurs through- out the year. 11