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Brown trout in the 251 to 300 mm size range ingested significantly <br />more diptera than did rainbow. There were no other significant <br />differences in the amount of any other food utilized. <br />Larger percent volumes of diptera larvae were recorded for stomachs <br />of rainbow captured in the canyon area; percent volume of diptera was <br />similar for trout collected in the open and inflow areas. Apparently <br />this food was more available to rainbow in the canyon area. Data <br />relative to the bottom fauna of Flaming Gorge Reservoir indicate that <br />dipterans are more abundant in littoral habitat in the canyon area <br />than in other portions of the impoundment. <br />Considering aquatic insects, excluding zooplankton, it is apparent <br />that as the size of the trout captured increased, the mean percent <br />volume of aquatic insects also increased (Figure 2). These data may <br />indicate that trout enter a new trophic level or become more oppor- <br />tunistic as they grow larger. Other workers have noted similar trends <br />(Swift 1970, Weidlein 1971, and Williams 1954). <br />Food items representing the order hymenoptera were taken incon- <br />sistently by rainbow and brown trout (Tables 2 and 3). Perhaps these <br />organisms were not as available or as abundant as other foods. <br />Differences in foods utilized by fish captured in pelagic and littoral <br />habitat showed that trout from littoral areas used significantly less <br />zooplankton and fish than trout captured in pelagic zones (Figure 3, <br />Table 4). Trout less than 250 mm (9.9 inches) from pelagic habitat <br />contained 22 percent more zooplankton than trout of the same size <br />collected in litoral habitat. Generally foods taken by fish from the <br />littoral waters were more varied than foods of the pelagic fish. <br />Borgeson (1966) stated that good trout growth is associated with a <br />good food supply. Age-growth statistics presented by Varley, <br />Regenthal, and Wiley (1971) show that growth of rainbow trout is <br />better than average throughout Flaming Gorge Reservoir. Growth of <br />brown trout is comparable to that of rainbow (Varley, unpublished <br />data). <br />12