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8 I I I I I I I I I I I I I I I I I I I LaGory, K. E.1, J. W. Hayse I , T. Grand2, and S. F. Railsback2 J Environmental Assessment Division, Argonne National Laboratory, Argonne, IL; 2 Lang, Railsback, and Associates, Arcata, CA Preliminary Models of Colorado Pikeminnow Movement, Foraging, Growth, and Survival in Green River Nursery Habitat. Conditions in backwater nursery habitats are thought to play an important role in determining the reproductive success of endangered Colorado pikeminnow (Ptychocheilus lucius) in the Upper Colorado River basin. Age-O fish that use backwaters may be adversely affected by changes in river flow especially those that occur over a short time period such as the daily fluctuations caused by hydroelectric generation at Flaming Gorge Dam. A spatially explicit individual-based model is being developed that consists oftwo components: a physical habitat simulation and a fish simulation. The preliminary formulation for the latter component is presented in this paper. This model simulates the effects of changes in flow and habitat on the movement, foraging, growth, and survival of individual age-O Colorado pikeminnow in the Ouray reach ofthe Green River in Utah. Movement rules predict the involuntary movement offish in response to changes in flow and voluntary movements to adjacent habitats (mainstem or backwaters) in response to changes in habitat-specific potential fitness. Fish are assumed to swim at an optimal foraging speed, which is used to calculate (1) the quantity of prey encountered and consumed; (2) rate of energy expenditure; (3) daily growth rate; and (4) expected survival. Daily growth is calculated from estimated consumption rate and energy expenditures. Survival probabilities are calculated from the fish's length and condition; density of predators; and habitat conditions. The completed model should be a useful tool for evaluating the impacts on age-O Colorado pikeminnow of various Flaming Gorge Dam release scenarios. Work supported by Western Area Power Administration under Contract No. W-31-109-ENG-38 with Argonne National Laboratory and EPRI under agreement EP-P3215/CI529 with Lang, Railsback & Assoc. Nonnative Fish Control Brunson, R., G. Birchell and B. Williams Utah Division of Wildlife Resources, Vernal, UT Development of a Northern Pike Control Program in the Middle Green River, Utah. Effort to control Northern pike (Esox lucius) in the Middle Green River was initiated in late March of 2001 and continued through mid-June. 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 electro fishing. Trammel nets were regularly used in conjunction with electro fishing as a productive sample method. A total of251 northern pike were removed from the middle Green River from March through June 2001.