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Annual Recruitment A major consideration for a species in danger of extinction is whether recruitment is adequate to sustained the population indefinitely. Many times this is not the case, therefore, a significant thrust of the work done on the endangered Colorado River fishes has been to evaluate recruitment. Thus far a substantial body of information has been collected but due to the short period of record, great variability in sampling results, and the inability to as yet adequately determine adult popula- tion status or to trace strong year classes through the population, the long term Colorado squawfish population trend is yet unclear. Larval Sampling Larval fish sampling was first initiated by the CDOW in 1979 but it was not untU 1981 that techniques and effort were adequately advanced and extensive to provide reliable information on spawning success. The record is quite disjunct with some years. of extensive standardized sampling, others with less extensive survey-type collections. The best continuous record has been developed by CDOW on the lower Yampa where four continuous years of standardized sampling has been carried out. Two years of standardized sampling was conducted during 1981 and 1984 on the Green by CRFP and extensive sampling was conducted on the upper Colorado by both CDOW and CUP since 1981. Haynes et ale (1984) sampling showed the best production of larval Colorado squawfish during the high water years of 1983 and 1984 (Table 6). CUP sampling in the Green River during 1981 and 1984 did not demonstrate major differences but the 1984 catch rate was higher. Sampling in the Colorado River showed significantly higher incidences of larval Colorado squawfish during 1982. This was not refle<:ted in the Haynes et ale (1984) work. but they did colle<:t substantially more larvae during 1980. ~ 23