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1 <br />Pro) based on geomorphic reaches identified during the first workshop as the smallest <br />spatial scale. The Upper Basin was divided into three river segments comprised of the <br />Yampa/Green River (above the confluence), the Colorado River segment, and the <br />segment below the confluence of the Green and Colorado Rivers to Lake Powell. The <br />model was generated as specific as data would allow and included sex ratio, <br />survivorship means, and variances for larvae, YOY, 1-, 2-, and 3-yr-old fish and adults. <br />Initial population values for each age class as well as carrying capacity values for each <br />geomorphic section were also used as initiation values in all models. While the model <br />can be used in a very specific manner (e.g., to model only 2-yr-old fish in a particular <br />reach , it can also be arameterized to mode( the U er Basin as a sin le o ulation. <br />P PP 9 P P <br />Following the initial model development phase, workshops were held at Utah State <br />University and at Lake Powell to develop species-specific attributes and to identify data <br />sources for parameter estimation. Using that input, we identified approximately 21 data <br />sources that included sufficient data for some parameter estimates. We also identified <br />7 data sources that allowed us to make estimates of total or subpopulation estimates <br />for 3 of the 4 fish species (no data -exist for Upper Basin bonytail chub). Parameter <br />estimates and their sources are detailed in Tables 9, 10, and 12. <br />While we could find reliable data regarding adult survivorship and fecundity estimates <br />for most species, we were less successful in generating reliable estimates for <br />survivorship of larval, YOY or 1-, 2-, and 3-yr-old fish. Two and 3-yr-old fish have not <br />x <br />1 <br />