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variables that might now be limiting the populations of those fishes or might become important limiting factors as we endeavor to create conditions important to the recovery of the Colorado squawfish. In this report section, we briefly review those environmental variables, discuss their importance to the recovery of Colorado squawfish, and establish flow-habitat management objectives for each of the limiting factors that have been identified in the 15-mile reach. Those flow-habitat management objectives are based on the habitat requirements that we believe are important to the recovery of Colorado squawfish in the upper Colorado River, as directed by the Recovery Implementation Program. Physical habitat The 15-mile reach is occupied habitat for Colorado squawfish and razorback sucker, species that cannot be recovered and delisted if such habitats are not maintained and improved. In their earlier report, Osmundson and Kaeding presented data that indicated Colorado squawfish extensively use deep runs and pools in the 15-mile reach during July, August and September (see, for example, Figure 22, Appendix A). Although the present availability of such habitat may not now limit the size of the adult Colorado squawfiish population of the 15-mile reach, such availability nonetheless might prevent an increase in the population toward the recovery goals that need to be established. Because the numerical recovery objectives for the self-sustaining adult Colorado squawfish populations have yet to be established and the relation between the size of such populations and habitat quantity has yet to be determined, it is prudent to seek a near-maximum quantity of habitat for the adult fish and thereby eliminate the 7