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1 t 1 1 dam. A fifth scenario re-analyzes historic hydrology but begins with current drought- related low reservoir elevations to determine the effect of extremely low elevations on release temperatures (without selective withdrawal). Model results determine the temperature regimes which are possible throughout a given set of years, the effectiveness of incorporating selective withdrawal structures at the dam, and the effect of selective withdrawals on the reservoir's long term heat budget. The optimal range of temperature and releases needed to meet the temperature targets downstream at Delta identified in Osmundson's 1999 report are determined. This study indicates that it is possible to meet downstream temperature targets through incorporation of a multiple-level selective withdrawal structure. The effect of selective temperature releases on the heat budget of the reservoir is minor and of short duration, being dominated by other hydrologic and meteorological factors. Nonnative Fish Control Review of Middle Green River Northern Pike Control Williams, Ben and Ron Brunson Utah Division of Wildlife Resources, Vernal, Utah Effort to control Northern pike (Esox lucius) in the Middle Green River was initiated in 2001 and continued through 2003. The purpose of this effort is to develop an effective control program and reduce the density of adults such that predatory and competitive impacts on growth, recruitment, and survival of endangered and other native fishes are minimized. Northern pike were removed from known concentration areas of the middle Green River, including the mouth of Brush Creek, Cliff Creek, Stewart Lake Drain, Ashley Creek, Sportsman Drain and the mouth of the Duchesne River. Other habitats sampled were large, relatively deep backwaters and shoreline areas.. Sampling gear used included fyke nets, trammel nets and electrofishing. Trammel nets were used in conjunction with electrofishing as a productive sample method. A total of 248 northern pike were removed from the middle Green River in 2001, 42 in 2002, and 22 in 2003. Catch rates have decreased from 0.56 northern pike/net-night in 2001 to 0.03 northern pike/net-night in 2003, and 1.24 northern pike/electrofishing-hour in 2001 to 0.22 northern pike/electrofishing-hour in 2003. Four Northern pike were captured with razorback suckers in their stomachs during 2003 sampling. Mechanical removal has been shown to be an effective northern pike control method in the middle Green river.