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L fit parameters (p, ~, ~,) for all years were tested against models with a reduced parameter set. Akaike's Infonmation Criterion (AIC) was used as a guide in model selection; model fit was also assessed with tests in program RELEASE (Burnham et al. 1987). We were careful to guard against overfitting models with the sparse data available in this study and focused on those that gave reasonable estimates of parameters that were critical to understanding the status of razorback suckers in the middle Green River. Data analysis, larvae.-We present capture data for all species and also catch per unit 1 effort (CPLTE) for three native catostomids, razorback sucker, flannelmouth sucker Catostomus latipinnis, and bluehead sucker Catostomus discobolus. We also used data from 1993-1996 presented by Muth et al. (1998) to obtain a longer data series so that we could evaluate potential trends in capture rates. The CPLTE analyses were number of fish captured per hour of light trapping; average sampling time was about 8.5 hours. Total annual sampling effort was based on samples collected only after the first sucker larvae was captured each year. Capture dates of razorback sucker larvae were used to reconstruct timing and duration of hatching embryos and reproduction by adults in relation to flow and water temperature regimes. This approach follows Muth et al. (1998) except they used otolith increments to estimate hatching dates and growth rates of larvae. We back-calculated hatching dates for individual larvae by subtracting length of larvae at capture from average length at hatching (8.0 mm TL). We divided the difference by 0.3 mm, which was the average daily growth rate of wild larvae observed by Muth et al. (1998). The result was an estimate of the number of days since hatching, which was subtracted from the capture date. Time of embryo fertilization (spawning) was estimated by subtracting temperature-dependent times of incubation from hatching dates; incubation times were estimated from Bozek et al. (1990). Dates of incubation, hatching, and 10