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' us to distinguish which movements were most likely migrations to and from ' spawning sites. In 1986, spawning in the Grand Valley was estimated to have occurred between t 26 July and 5 August. In 1987, the single larva collected was estimated to ' have been spawned on 4 July. The 20-day period encompassing this date (24 June to 14 July) is assumed to be a reasonable estimate of the spawning period ' in the Grand Valley during 1987. Movements related to spawning were distin- guished based on this and a careful examination of fish locations during ' radio searches on dates prior to, during, and subsequent to these estimated spawning periods. Two of three radio-tagged squawfish in 1986 apparently ' t d i h s aye w t in the 15-mile reach during the estimated spawning period, whereas ' the third moved above the reach to the base of the Price Stub Dam. In 1987, four of the seven tagged fish moved downstream and out of the reach during or ' just prior to the spawning period and were located outside the reach during the spawning period; two, and possibly a-third radio-tagged squawfish stayed within the reach during the entire period. If all of these fish spawned, ' three of them probably did so inside the reach, two outside. The sixth fish, having moved in and out on two separate occasions during the estimated spawn- ing period, may have spawned either in or out of the reach. Interestingly, the three fish that stayed within or moved above the reach during the spawn- ing season in 1986 all moved downstream and out of the reach during the 1987 spawning period. One was located at the base of the Redlands Diversion Dam ' (GU RM 3.1), another at Walker Wildlife Area (CO RM 163.7), and the third ' near the Utah state line (CO RIM 130.1). All three of these fish returned to 1 the 15-mile reach during or shortly after the estimated spawning period. 18