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The Diet of Rainbow and Brown Trout from Flaming <br />Gorge Reservoir, 1964 through 1969 <br />by <br />Robert W. Wiley, Wyoming Game and Fish Department <br />John D. Varley, U.S. Fish and Wildlife Service <br />ABSTRACT <br />Data are presented relative to the use of food by trout during the first <br />six years of impoundment of Flaming Gorge Reservoir. A total of 1,343 <br />stomachs from rainbow trout, 64 from brown trout and six from cut- <br />throat trout were analysed during the project. We found the primary <br />food of rainbow trout to be zooplankton. Brown trout included zoo- <br />plankton as a major part of their diet and also used significant quantities <br />of forage fish. It was apparent that zooplankton sustained both rainbow <br />and brown for a good portion of their life. Too few cutthroat were <br />sampled to make comparisons justifiable. <br />We described five major food items, that is those items that comprised <br />generally more than 15.0 percent of stomach volume: zooplankton, <br />organic debris, fish, diptera and hymenoptera. Organisms representative <br />of the order hymenoptera were identified only from occasional <br />stomachs. The use of forage fish declined down-reservoir during the <br />study and was positively correlated with forage fish abundance. Gen- <br />erally, zooplankton was an important food item in all areas. Dipterans <br />were more common in the stomachs of rainbow captured in the canyon <br />area. <br />No intensive intra-specific competition for food was demonstrated <br />although rainbow and brown used comparable quantities of zooplankton <br />in all areas. Growth of each species was better than average and we <br />concluded that a positive correlation existed between food availability