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., <br />One hundred thirty-two pike were captured from the Yampa subpopulation in May through <br />November 1988-1990 and examined for stomach contents. Thirty-four percent of the stomachs <br />were empty in spring, 14%were empty during the summer and 30% in autumn. Diet <br />compositions were similar for both subpopulations (Figure 2) except that squawfish predation <br />was not evident in the Yampa River. Young-of--the-year, one- and two-year old squawfish were <br />(and are) extremely rare in the Yampa system during- summer and fall. Because of their <br />unavailability in this area, we did not expect to find them in the diets. The number of cyprinids <br />declined from 1.4 fish per stomach in spring to 0.4 in autumn, whereas suckers increased from <br />0.3 per stomach in spring to 0.9 in autumn (Figure 3). <br />Consumption Estimates <br />Model simulations predicted that a population of 1,000 northern pike would consume 188 kg of <br />Colorado squawfish per year, based on observed diet information wherein only age-4 northern <br />pike ate Colorado squawfish (Figure 4). Seasonally, the biomass of juvenile Colorado squawfish <br />consumed by 1,000 pike was highest during spring and summer, lowest in autumn (November- <br />January), and intermediate in winter (February-April). Numerically, the highest predicted losses <br />of age-1 squawfish occurred during spring (59,097 1-g fish) followed by 21,885 2.8-g yearlings <br />during summer. If all predation on squawfish was directed exclusively on age-1 fish, 102,725 <br />would be lost annually to a population of 1,000 northern pike. These results should be viewed <br />as a first approximation because of the uncertainty in our diet information due to the small <br />sample of pike stomachs. <br />