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more similar to each other than conspecifics found in other upper basin locations. Their measurement of fin placement described much of the variation in their analyses. Although a suite of measurements were collected from each chub captured, the proper measurement in the field that referenced fin placement was not taken (because these measurements were not defined prior to the initiations of this study). All the juvenile and adult chubs referred to as Gila spp. in Report C displayed humpback tendencies and should probably be treated as a humpback chub from a management perspective. It is the contention of the authors, however, that these fish should be identified as something other than a pure or classic humpback chub. Putative roundtail and humpback chub were often collected in the same trammel net or occupying similar if not the same shoreline habitats while electrofishing (each of these sites is only 0.5 - 1.0 km in length). The Joe Hutch site, at RK 256, is the only location in which "typical" humpback chub were collected with any regularity. During the present study, three chubs with G. elegans tendencies were collected: one at Joe Hutch in 1992 and two at the Coal Creek site (RK 232.8); one in 1994 and 1995. All nine recaptured chubs were collected at their original capture location. Whereas the f ~l sampling program tends to select for sedentary individuals, considerable. electrofishing effort is ` '' expended between the intensively sampled areas. The low recapture rate is more likely due to ~_ ~~ __ low sampling effort and population dynamics (recruitment /mortality) than fish moving away ` ' from previous capture locations. Long term monitoring trammel net catch rates suggest the number of adult sized chubs in Desolation declined as result of the poor recruitment prior to 1993. Catch rates were lowest in 1996. Since UDWR sampling began in 1985, juvenile chubs have been collected in 1989, 1990, 1994 and 1995 with gaps in the population structure (age 1 and age 2 fish) the other years. In 1989, the length frequency analysis indicates the presence of a relatively weak 1988 year class, a stronger 1987 year class, and evidence of strong recruitment from the years prior to 1986. The 1993 year class appears to have recruited to a juvenile size in the most substantial numbers since that time. Densities of adult Gila spp. in Deso/Gray canyons are moderate in the context of upper basin populations. In Westwater Canyon, combined Gila spp. average trammel net catch has exceeded 0.8 fish /net hr for the years 1992-1996 -roughly four times-the catch rate recorded in Deso/Gray during the same time. Reported catch rates at Black Rocks on the Colorado River (McAda et al. 1994) also greatly exceed those reported here.. Conversely, Deso/Gray catch rates far exceed those reported for Cataract Canyon; 1985-1988 (Valdez 1990). The Deso/Gray population was apparently rejuvenated in the late 1980's (as determined in UDWR 1989 sampling) with several consecutive pulses of recruitment. This increase in chub numbers follows the extremely high flows of the early to mid-1980's. Since that time recruitment has dwindled and adult catch rates subsequently dropped presumably due to an extended period of low flow (1988 - 1992). Recruitment was documented during this study in. 1994 and again in 1995. Preliminary results from sampling in 1997 indicated that the adult population densities are increasing in response to this recent recruitment. Again, a period of moderate to high flows in 1993, 1995 and 1996 appears to coincide with this recruitment. ,f ~_ xvi.