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-69- Eyed eggs were unaffected by water temperatures as low as 32° F., and hatch- ing success was high.. Green egg mortality was in excess of 95% when ,subjected to 32~ F. water temperatures. Control groups used fn green egg experiments were placed in a hatchery incubator at a water temperature of 46° F., and these eggs eyed 96~ and hatched 93% of the total eggs. The green eggs placed in .the hatchery at 46° F., and 40 Rod Creek at 42~ F. required in excess of 400 temperature units to the eyeing stage. Of those eggs placed in river water at 32~ F., the majority were dead by the time 36 temperature units had been expended, During natural spawning periods, however, the eggs would not be deposited on redds while the water temperature was 32° F.; kokanee normally spawn at water temperatures of about 40® F. with eggs usually deposited in springs or seepage areas having temperatures higher than this. Using the temperature data obtained from the Intermountain Chemical Company, Graph I, page 15,-there is an average over a three-year period of 159 temperature units expended between 40 and 35® F. in the area where spawning redds were to be established, This 159 temperature unit ex- penditure is approximately 2.5% of the .units required to eye kokanee eggs. Whether this amount of temperature units is sufficient to allow the kokanee eggs to develop to a point where they can withstand water temperatures of 35® F. and below is not known. The possibility of establishing kokanee spawning runs in the Green River is further complicated by the Seedskadee Project. Under projected operations, the river flow will. be drastically reduced during the normal spring run-off period. Run-off waters will be stored in Fontenelle Reservoir far irrigation purposes later in the year. This reduced water flow in the Green River will increase the effect of the heavy silt load carried by the Big Sandy River and intermittant streams entering the Green River below Fontenelle Dam .and above the kokanee spawning area. This change in river conditions will occur just after kokanee fry emergence. Projected reservoir operation will eliminate any reproduction of kokanee in the reservoir proper. Under projected operations the reservoir water level will be dropped in January, approximately 2 months after the kokanee have spawned in the shallow areas, and will not return to full condition until late summer. This fluctuation would strand any spawn above the water level approximately 6 to 7 months. Kokanee, if planted in the Flaming Gorge Reservoir, would have to be maintained by annual stocking. These kokanee populations would be relatively unavailable to the fishermen because of their size for the first two years of their lives. The third and fourth, possibly fifth, years are the only years in which any noteworthy return to the creel would occur. The life cycle would be completed in the fall of the fourth, or fifth year after spawning, removing the mature fish. It would not be advisable to stock a fish which would compete with other species of sport fish for-food and space and provide angling for only two years of their life, if these fish have to be maintained by stocking because of conditions which eliminate the natural reproductive potential,