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5 Spring - Adult Colorado squawfish: For all three rivers combined in 1987, a total of six Colorado squawfish were collected and seven more observed, compared to 19 collected and four observed in 1986 (Table 3). Catch rate indices ranged from 0.00 to 1.55 fishlhr in 1987 compared to 0.00 to 2.01 fish/hr in 1986. Too few Colorado squawfish have been sampled in either the Colorado or White rivers to make any meaningful comparison between 1986 and 1987. The most notable difference was apparent in the three Yampa River stations, where the total number of Colorado squawfish collected declined from 17 in 1986 to 5 in 1987. This decrease was attributed to difficulty in sampling due to turbid water conditions and problematic generator operation. Sampling efficiency in the Yampa River in 1987 was poor relative to 1986 as a result. With the exception of one river reach (Code 9) in 1986, standard deviations were equal to or larger than the mean clf estimates, indicating considerable sampling variation. River reaches within the Yampa were combined to estimate an overall mean catch rate in each year. In 1986 the mean clf was 1.06 fish/hr (CV=89%); in 1987 the mean clf was 0.47 fishlhr (CV=145%). It seems logical that Colorado squawfish observed but not captured should be included in catch rate esti- mates since: (1) identification is relatively reliable by experienced field personnel; (2) records of observed fish are only made with a high degree of certainty; and (3) it is unlikely that captured and released specimens are observed downstream. Recapture or sighting of a recently tagged Colorado squawfish within the same river reach has yet to occur in Colorado. Includ- ing observed and captured Colorado squawfish in catch rate estimates for the appropriate river reaches in the Yampa, overall mean catch rates were 1.20 fish/hr (CV=73%) in 1986, and 0.72 fish/hr (CV=142%). These pooled esti- mates still demonstrate a decline between the 2 years, but the variability associated with the estimates suggests no statistically significant differ- ence exists. In 1986, 37 northern pike, Esox lucius, were observed during monitoring efforts in the Yampa River. In 1987, seven northern pike were observed. No measurements were taken on the few specimens actually captured, but it was apparent that the pike population consisted of at least 2-3 year classes in both years. Discussion The predominant attribute of monitoring results collected thus far has been the high degree of variability associated with c/f estimates, regard- less of pooling. Despite some very apparent differences in the data, statistical testing would indicate no significant difference existed. With regard to the objective of monitoring the status and trends in Colorado squawfish populations in Colorado, sampling variation has diminished the validity of conventional statistical comparisons. This seems due to the rarity of Colorado squawfish and the sampling methods available for monitor- ing. Only an order of magnitude change in catch rates would provide statistically meaningful results. As long as the status quo exists, biological interpretation of monitoring results will have to rely on the expertise and intuition of biologists familiar with the species and the river system.