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Table 4. Young-of-year Colorado squawfish collections, Colorado and Yampa river study areas, 1979-82a. Study area 1979 1980 1981 1982 Total Colorado River Stratum H 8 66 1 14 89 Stratum K 0 11 0 2 13 Totals 8 77 1 16 102 Yampa River Stratum 1 46 23 20 89 Stratum 2 0 0 0 0 Stratum 3b 0 0 0 0 0 F Stratum 4 0 0 0 0 Stratum 5 0 0 0 0 Totals Ob 46 23 20 89 aCombined collections by Nongame Research and Northwest Regional personnel. bOnly stratum 3 sampled in 1979. For the purposes of this investigation, the earliest dates during 1979-82 when water temperatures reached or exceeded 18, 20, and 22 C - along with our earliest estimated spawning dates are summarized in Table 5. -For those years for which temperature records are available, except 1979, spawning is closely correlated with the earliest date of record when the water temperature reached or exceeded 22 C. In 1979, spawning in the Colorado River possibly occurred as early as 29 June, coinciding with a temperature of 18 C but nearly a month prior to 22 C. This suggests that water temperature at the spawning site may differ from the site at which the temperature was measured or that 1 or more fish spawned at the lower temperature. The relationship between decreasing flows and the timing of the spawning is apparent; however, a quantifiable relationship between relative level and duration of flow and spawning success is less obvious. Further analysis will await 1983 collections and more detailed data review, including interpretation of capture-per-unit-of-effort values, and will be deferred for the final report.