Age-0 Colorado squawfishPtychocheilus lucius(N= 11,379) were captured as larvae and postlarvae in drift nets and seines in the Green and Yampa rivers from 1979 to 1988. Larvae were captured in drift nets (N= 601) for 2–6 weeks in June and July. Small postlarvae (N= 3,079) were captured by seining shoreline habitats in July and August. In September and October, postlarvae were most abundant (N= 6,459) in low-gradient reaches of the Green River. Catch data indicated that the postlarvae moved from the Yampa and Green river spawning areas and were concentrated about 150 km downstream by autumn of each year. Spring sampling indicated that young fish (N= 1,240) overwintered in areas occupied the previous autumn. Postlarvae captured in the Green River (N= 5,043) most frequently occupied shoreline embayments (backwaters) that were relatively warm (mean, 17.0°C), deep (mean, 38 cm), large (mean, 826 m2), and turbid. Abundance and size of young Colorado squawfish in the Green River were inversely correlated with high summer and autumn flows, which inundated nursery habitats. Seine catches of young squawfish in 4 years of sampling the upper and lower Green River in autumn and the following spring were not reliable in assessing overwintering mortality of age-0 Colorado squawfish, presumably due to differences in capture vulnerability between seasons. Survival of small fish in spring indicated their tolerance of prevailing winter conditions.