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f i I~ ~_~ assigned an energy density of 1196 cal (4991 J} per gram wet body mass to Colorado squawfish and other re Hewett and Johnson 1992. The ener densit of northern ike was treated as a p Y ( ) gY Y p ' constant 1049 caVg (4391 J/g; Wahl and Stein 1991). Model Simulation We ran the model to predict daily consumption over 365 d for each age class of pike, beginning on 1 May. Growth for each cohort was fitted to spring (May-June) and autumn (October) age- specific body mass estimates. A baseline run, using age-specific diet composition from field data, was compared against six other simulations which assumed that Colorado squawfish represented 1%, 2%, 3%, 5%, 10%, or 25% of the diet by weight for all age classes throughout the year. Spatial-temporal overlap of juvenile (age-0 to age-3) Colorado squawfish indicated that the opportunity for predation remained throughout spring and summer in backwater habitats, and that overlap was probable during winter when all species were concentrated in scarce deep pools used as overwinter habitat. Seasonal consumption by individual pike from each age class was scaled up to seasonal, population-level predation rates by multiplying age-specific individual consumption times the proportional age structure of pike found in field collections. We assumed the size and age structure from our field collections were representative of the population since pike were captured with trammel nets, by electrofishing, or by using electroshockers to drive pike into trammel nets. Since accurate estimates of northern pike abundance in the Ouray reach were not known due to extremely low recapture events, population-level predation rates were computed for 1,000 pike conforming to the observed size and age distribution. ~ a