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. , 11 sQuawfi sh were collected in the 15-mil e reach be low the confl uence of the Gunnison River (54 samples). The 1982 to 1984 catch rate of young-of-year Colorado sQuadish in the 10-mile reach immediately downstream of the confluence of the Gunni~ River (river miles 160 to 170) warranted classification of this reach as a 'Ymmg-of-Year Nursery Area' by the Biology Subcommittee of the Upper Colorado River Basin Committee (1984). Nonspawning Milt Occurrence Although the ~ling effort was similar between the reaches upstream and downstream of the Gunnison. over 60 percent of the adult-size Colorado sQuawfish collected during spring surveys by the Fishery Project (Hiller et al. 1982, Kaeding and Omundson 1987) came from the upstream 15-mile reach. Kaeding and Osmundson (191n reported that adult Colorado sQuawfish catch rates in the upstream 151dle reach were twice as high as those in the adjacent downstream river reach. Adults were most abundant in a 0.6-mile segment (river miles 174.4 to 175.0) of tae 15-mile reach during high water, particularly in two gravel pit ponds that ~accessible during high flows. These fish may have moved into these ponds tD feed and rest, or they may have been attracted to the warm, productive emrironments that the ponds provided (pond temperatures were as much as 10.50 C ~r than the adjacent river). Some of the sQuawfish captured from one pond were 1ll!11 tuberculated by June 3, when nearby river temperatures were only 100 to 1]1 C (Kaeding pers. comm.). It has been hypothesized by some investigators tlIat thermal energy units above those provided in the mainstream are important ttI gonadal maturation. If this is true, then access to these sheltered off~nnel pools may be very important to successful spawning in the upper reaches.r the Colorado River. Discussion and Conclusions The importaOC!of the IS-mile reach from Palisade to the confluence of the Gunnison RiverlUst take into account the fact that the Colorado sQuawfish is currently ~red and restricted to less than 30 percent of its original range. The ~ado River subbasin population shows particular signs of further decline; catdtJer-unit effort rates for larvae, young-of-year, and adult Colorado s~sh are low (Archer et al. 1986). Furthermore, the small numbers of young obsenld each year may not be sufficient to maintain a viable adult population. AlHtional loss or degradation of remaining habitat will exacerbate the problems de species is currently experiencing in the Colorado River. Field studies UllIducted over the past several years by the Service (see above) document theBlof the 15-mile reach by several life stages of Colorado sQuawfish (i.f.. adults and larvae>. In 1984, the Upper Colorado River Basin Biology Subcalittee identified river miles 170 to 180 of the IS-mile reach above the Gunibon confluence as a 'suspected Colorado sQuawfish spawning area,' This detenuininon was based upon: (a) the collection of ripe male and female fish in the n!Eb above Gunnison; (b) the observation of radio-tagged fish in