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It should be notedt however, that these heavy spring flows have tended to delay spawning about two weeks and depressed maximum temperatures which has resulted in smaller young-of-the-year fish at the end of the growing season. Survival of those smaller fish may be reduced to the extent that the increased production may be negated. In the Colorado Rivert the only other area where quantitative sampling has been carried out every year for the past three years, the opposite relationship appears to have been observed with the highest production of larvae occurring in 1982 during a runoff year closer to average. In the Green Rivert extensive sampling was carried out during the two contrasting years, 1981 and 1984. Substantially more larvae were collected per sample (0.56) in 1984 than during the low flow year of 1981 (0.12). In the Green Rivert flows have ~sually dropped from 20-30tOOO cfs to 10- 20,000 cfs at the commencement of spawning and continue to drop precipitously to 5-7,000 cfs toward the conclusion of spawning (Table 4). Daily maximum water temperatures are usually 20-220C and may become as high as 25-270C by the conclusion of spawning. In the Yampat peakrun-off generally approaches 15tOOO cfs and has declined to 5-8,000 cfs by the onset of spawning with flows continuing to decline to 1-2,000 cfs by its conclusion (Table 3). Temperature regimes at the Ya1l1pa spawning areas are similar to the Green though daily fluctuations and maximums have often been greater. Peak flows in the Colorado ranging between 20tOOO-30tOOO cfs have generally declined to 15,000 cfs by the onset of spawning and continue to recede to 4,000 cfs toward its conclusion (Table 5). Temperatures remain a few degrees cooler than the Yampa and Green with maximums seldom exceeding 250C. 20