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fish per mile. For the river as a whole (Palisade, Colorado to the Green River confluence, Utah), size of the subadult and adult population was estimated at around 600-650 during the period of study. A relatively large number of subadults (300-400 mm TL) were found in the lower reach during 1991. Scale analyses indicated these fish were from three year-classes, hatched in 1985, 1986, and 1987. By 1992, these fish were distributed throughout the river system. Trammel-netting catch-per-unit effort in the upper reach steadily increased over the four years of study. Though catch rates of larger adults (> 550 mm long) did not significantly increase, catch rates of subadults and young adults (< 550 mm long) increased five-fold. Size- frequency analysis of lower-reach fish indicated the 1985-1987 cohorts were the strongest year classes produced since at least 1977, and no similarly strong year classes have been produced since 1987. Catch rates of larvae and YOY in the Grand Valley also indicated that reproductive success in 1986 and perhaps in 1987 was relatively high, and all other years through 1994 had comparatively low catch rates. Until this recent pulse of young adults was produced, the vast majority of adults were found in the upper reach; the lower reach contained almost exclusively individuals < 500 mm long. Thus, in recent years, the bulk of the adult population was contained in the upper reach. There, very few individuals < 450 mm long are found, indicating that recruitment to the upper reach subpopulation occurs almost entirely from colonization of young adults migrating there from the lower reach. In contrast, size frequencies recorded during the mid 1970's indicate that significant recruitment in the upper reach may formerly have occurred via young rearing within the upper reach. Though some level of recruitment appears to occur every year, the Colorado River population of Colorado squawfish is probably sustained by strong year classes that occur very infrequently. Though adult survival rate is likely fairly constant from one year to the next, recruitment is highly variable. Long-term, average, annual rates of recruitment are unknown and therefore it is difficult to discern whether recruitment balances mortality over the long term. Given the current low population size in comparison with historical accounts that suggest the species was formerly abundant, it is likely that recruitment has not kept pace with mortality. However, this population appears quite capable of recovering on its own if the frequency of strong year classes can be increased. This will require the improvement of environmental conditions that currently limit reproductive success and survival of young. v