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' Following the initial model development phase, Crowl and Bouwes (1998) conducted workshops at Utah State University in Logan, Utah, and in Page, Arizona, to develop species-specific model attributes and to identify data sources available for parameter estimation. Using this input, they identified approximately 21 data sources that included sufficient data for some parameter estimates. They also identified 7 data sources that allowed them to make estimates of total or subpopulation estimates for three of the four species. Parameter values are detailed in Table 5. Crowl and Bouwes (1998) found reliable data regarding adult survivorship and fecundity estimates ' for most species, they were much less successful in generating reliable estimates for survivorship for larval, YOY or 1-,2 and 3-yr old fish. Two and three year old fish have not been targeted for specific sampling in most studies. While numerous studies exist to sample larval and YOY dynamics, the study designs were inadequate to allow for robust, reliable estimates of survivorship. A few notable mark-recapture studies had been completed, but were very small in scope making extrapolation very uncertain. Crowl and Bouwes (1998) added to this information base by including population estimates for some of the subpopulations of Colorado squawfish. 1 u 1 1 1 Table 5. Parameter values in the Crowl and Bouwes (1998) life-stage model for the four endangered Colorado River fish: Colorado squawfish, razorback sucker, humpback chub and bonytail. LIFE STAGE COLORADO SQUAWYISH RAZORBACK SUCKER HUMPBACK CHUB BONYTAIL survival /year SD survival /year SD survival /year SD survival /year SD egg/larval 0.010 0.001 0.010 0.001 0.010 0.001 0.010 0.001 age 0-1 0.140 0.050 0.140 0.050 0.050 0.005 0.140 0.050 age 1-2 0.300 0.050 0.220 0.050 0.100 0.050 0.300 0.050 age 2-3 0.400 0.050 0.370 0.050 0.150 0.050 0.400 0.050 age 3-4 0.600 0.650 0.550 0.050 0.760 0.050 0.600 0.050 adult 0.800 0.040 0.700 0.020 0.760 0.020 0.800 0.040 14