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feeding to 57% after feeding. Survival of fish denied food for > 20 d after first feeding was low. Point of no return was between 17.5 and 20 d. Low, stable flows that simulate natural hydrographs may enhance growth, survival, and recruitment of early life stages of Colorado squawfish by increasing water temperature and food abundance in regulated rivers of the Colorado River basin. Otolith analysis may be a tool to evaluate various hypotheses about recruitment regulation in wild populations of Colorado squawfish. Otolith microstructure of Colorado squawfish was investigated under different temperature and feeding regimes to determine validity of daily increment aging and patterns of otolith growth. Sagittae and lapilli formed prior to hatching. Otolith increments were deposited daily after hatching in fish in constant 22°C and fluctuating (± 2.5°C d-') 18, 22, and 26°C temperatures. Otolith increments were clearer and counts were more accurately estimated in fish reared in fluctuating than in constant temperatures. Lapillus diameters of slow growing Colorado squawfish were significantly larger than similar-sized fast growing fish, indicating that fish and otolith growth rates were not proportional. Somatic growth of starved larvae generally ceased immediately but otolith growth continued for up to 15 d. Otolith growth was reduced for up to 5 d after starved fish began to feed. Timing of starvation and reduced growth may not be accurately recorded by reduced otolith increment spacing. Otolith increments deposited during starvation periods were of low contrast and may indicate periods of low food abundance in the wild. Otolith analysis will be useful for elucidating age, growth, and recruitment patterns of young Colorado squawfish. Recruitment of age-0 Colorado squawfish in the Green River, Colorado River basin, was investigated with otolith analysis to evaluate relative importance of physical v