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exogenous feeding was shorter at higher temperatures. Differences in lengths of larvae <br />at hatching and at 7-d at the various test temperatures were small and not considered <br />ecologically significant. Tolerance of a relatively wide range of warm water temperatures <br />by Colorado squawfish embryos and larvae may reflect the historically variable Colorado <br />River environments in which the species evolved. Cold summer water temperatures <br />caused by mainstream dams have eliminated Colorado squawfish from portions of its <br />historic Colorado River basin range. Water temperatures that more closely reflect historic <br />regimes are necessary to restore self-sustaining populations of Colorado squawfish in <br />those areas. <br />Growth and survival response of Colorado squawfish larvae up to 42 d-old was <br />determined under fluctuating and constant 18, 22, 26°C, and 30°C water temperatures and <br />at five different food abundance levels. Optimal growth was at the highest water <br />temperatures and food abundance levels. High growth was observed at temperatures > <br />25°C with moderate food abundance; growth was lowest under lowest food rations and <br />highest temperatures. Survival of larval Colorado squawfish was optimal at 26.2°C and <br />235 nauplii•fish-'•day'; model solutions indicated that survival was > 90% at <br />temperatures ranging from 20 to 30°C with moderate food abundance. Survival was <br />lower at 18°C even in the presence of high food abundance and was lowest when food <br />abundance was low and temperature was high. Neither growth nor survival was <br />significantly different between fluctuating or constant regimes. Colorado squawfish <br />larvae denied food for 5, 10, or 15 d after first feeding could have begun (6 d), had <br />survival greater than 87% which was equivalent to continuously fed controls. Survival of <br />fish denied food for 17.5 d after feeding could have begun declined from 84% before <br />iv <br />