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<br />immediately downstream, and the lower 2.2 miles of the Gunnison River <br />between the Redlands Diversion Dam and the confluence. <br />1 <br />Distribution and relative abundance of young-of-the-year (YOY) Colorado <br />' squawfish were estimated by seining backwaters with 3-mm-mesh beach seines. <br />Each year, two samples were collected from each of two backwaters in each 5- <br />mile reach. The 1986 effort was conducted on 22 September and 1 October; <br />' the 1987 effort, on 22 and 23 September. Collected fish were preserved in <br />10% formalin in the field and identified in the laboratory. To determine <br />relative abundance, the surface area seined was measured and the number of <br />squawfish collected per 100 square meters seined was calculated. The study <br />' area sampled for YOY included the 15-mile reach and the adjacent 18-mile <br />' segment of the Colorado River immediately downstream. <br />Microhabitat use of adult Colorado squawfish and razorback sucker was <br />' estimated by measuring depth, velocity, substrate and temperature at the <br />locations of radio-tagged fish. Possible spawning sites were identified by <br />the aggregation of ripe adults during the spawning season and, for squaw- <br />fish, by the subsequent collection of larvae. Unfortunately, techniques for <br />identifying razorback sucker larvae have not yet been developed. Post- <br />hatching age of collected squawfish larvae was calculated using total <br />lengths of individual larvae in age-length equations developed by Haynes and <br />Muth (1985). Spawning date was then estimated by subtracting four days from <br />the estimated hatching date. Four days was considered the mean embryo <br />incubation time, based on the 3.8-5.0-day range reported by Haman (1981) <br />' for fertilized eggs of hatchery-reared squawfish incubated at 20-24 C. <br /> <br />