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50 <br />• o Significant discharge fluctuation should be avoided during winter, especially <br />during ice formation and ice breakup periods. <br />Wick and Hawkins (1989) reported discharge fluctuations to disturb <br />Colorado squawfish during winter periods. Flows are already at a <br />season low on most rivers, and additional changes or depletions in flow <br />can disrupt slow velocity areas used by Colorado squawfish. Low flow <br />habitat is thought to be necessary to provide an area where little caloric <br />expenditure is required, water is slightly warmer than in main channels, <br />ice cover offers protection from overhead predators, and food availability <br />is highest. Periods of ice formation are especially sensitive since a <br />portion of the already low streamflow is being tied up in ice formation. <br />4 Ice break-up is critical because it is in itself disruptive to fishes and the <br />channel. <br />Humpback chub. <br />o No data are available regarding habitat availability-discharge relationships. It <br />should be noted, however, that young-of-year humpback chub prefer eddy <br />habitat, thus flows providing adequate eddy areas during summer and fall <br />would be desirable in reaches inhabited by humpback chub. <br />Holden (1980) reported eddy habitat to be preferred by young of year <br />humpback chub. <br />40