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~ 17 an artifact of stocking of hatchery raised squawfish in Kenney Reservoir. The period studied using ISMP guidelines thus far has been a period of below normal precipitation. Ideally, data should be collected over the entire cycle of wet and dry years. The timing of spawning and extent of the growing season where water temperatures are in excess of 13 degrees C can be critical to survival of YOY Colorado squawfish. In 1986 when spawning occurred later and water temperatures cooled earlier, the average length of YOY squawfish in September was only 29 mm, compared to 36 to 43 mm in other years. Overwinter survival and subsequent recruitment can be dependent on size of post larval squawfish and their lipid contents as they enter the winter season (Thompson 1989). Curiously, most of the juvenile/ adult squawfish caught in 1989 were of the 1986 cohort (McKay and Hawkins 1990) when summer flows were cool and high. However, while the summer and fall conditions of 1986 appeared to be detrimental to continued growth of post-larval squawfish, Valdez (1990) found that this cohort experienced faster growth than other age classes when conducting overwinter survival sampling the next spring. Based solely on ISMP data we offer two additional explanations. Of these first five years of the ISMP, 1986 was the closest approximation of a "normal" water year, and the catch rates of non-native, sympatric species from backwaters were relatively low as has been documented elsewhere in the basin (McAda and Kaeding 1989). The question remains, Why was the 1986 year class the first to show up strongly in the electrofishing collections? Although the ISMP was initiated in 1986, YOY sampling, following various protocols has been conducted since 1979. Both the biological and physical data collected those years must be reviewed to better understand why the 1983, 1984 and 1985 squawfish cohorts were not represented as strongly as the 1986 cohort in the ISMP electrofishing collections. From 1987 through 1990, late summer and fall flows were low and warm in the lower Green River and YOY squawfish were relatively (compared to 1986) large. The 1987 cohort has been detected (using McKay and Hawkins' findings relative to the 1986 cohort as a basis) in the 1990 spring electrofishing length frequency histograms. It remains to be seen if 1988, 1989, and 1990 year classes are well represented in future spring electrofishing samples as were fish spawned in 1986 and 1987. A significant increase in flow from 25 to 50% after water temperatures have increased to 200 C may result in increased spawning (Nessler et ale 1987). Catch rates of post larval squawfish from the lower Green River (1986-1989) also supported