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The highly turbulent, harsh habitat where the humpback occured harbored fewer fish species than most areas of the rivers. This suggests the humpback lives in a highly specialized environment that excludes other species, particularly exotics. Temperature was a very critical environmental factor for humpback chub. Areas occupied not only were very unique and limited physically, but is required specific temperature for reproduction. Temperatures - v of C needed to be attained for initiation of spawning and best hatching success and larvae survival occured-at about 20°C. Thus, areas occupied now included the relatively warm Little Colorado River in the ' lower basin and areas of the Upper Colorado River where the needed temp- eratures still occured. Areas where humpback chub have been extirpated included those areas inundated by dams and those areas impacted by cold water releases below reservoirs, such as Flaming Gorge Canyon in the Green River. Juvenile and adult humpback chub seemed to be associated with some of the shallower portions of the deeper river sections. In many of these areas a shelf area existed along the edges of the deeper water which provided a resting and feeding area for the humpback. Also, many pockets, depressions and crevises occur in the bedrock boulder substrate which provided isolated microhahitat favored by humpback chub. Although adult humpback were quite capable of navigating the swift turbulent water, as evidenced from radio tracking efforts, most time was spent in pockets and back eddies adjacent to the deep, swift water. Reproduction was not directly observed in the wild but it is suspected that spawning takes place within the boundries of the deep, swift water canyon. All ages of chub were found in the few areas where they occured, which supported the conclusion that successful reproduction and recruit- ment was taking place. Pockets of clean rubble-gravel areas are probably utilized for spawning within the immediate canyon area and in upstream associated areas. Young fry have been taken in and around the boulder and depression of the bedrock areas within the deep canyon itself which suggests the conclusion that all life stages are occuring within the limited area of known adult populations. Migration and Movement Tagging and radio tracking programs were conducted in the Black Rocks area of the Colorado River to determine movement patterns of humpback chub. Sixteen of 218 fish tagged in the Upper Colorado River were recaptured 1-434 days after release. All but one of the recaptured fish moved less than 0.5 mi from their release site. Eight fish equipped with radio transmitters also demonstrated very little movement up or downstream. Generally, we concluded that humpback chub do not make migrational movements and tend to reside throughout the year within a very limited 1/2 to 1 mi stretch of river. The return of some tagged fish, both dangler tagged and radio tagged, to their original site of capture after release fn slightly different micrahabitats suggested that Lhey may have a home territory or range within the confined river stretch which they occupy.