8182 - Laserfiche WebLink

Home Browse Search

twice individuals were captured from the same pool or eddy where a Colorado pikeminnow was captured. The largest individual captured had consumed a flannelmouth sucker that was about 300 mm TL. There was no evidence of reproduction by northern pike in the regulated reach of the Green River, although the 112 mm TL individual captured in a backwater seine sample in Island Park may indicate downstream reproduction. Smalhnouth bass were rare in Lodore Canyon samples; one was captured by electrofishing and two by seining. Single specimens were captured in one backwater located in the lower Yampa River and one backwater in Island and Rainbow parks samples. With the exception of one 180 mm TL individual, all were < 100 mm TL. Small individuals captured in Lodore Canyon could have originated from the Yampa River because they were captured in a backwater just upstream of the confluence. Channel catfish was the most abundant (N = 58) non-native fish predator in the regulated reach of the Green River, and was particularly common in reach 4. Channel catfish averaged 297 mm TL (195 - 457), and all were sampled with either electrofishing gear or by angling. There was no evidence of reproduction by channel catfish in the regulated reach of the Green River because no small individuals of that species were noted in backwater seine samples or in drift net samples. Green River water temperatures: observations, models, and predictions.-Temperature of releases from Flaming Gorge Dam increased in spring when penstock gates were moved from the reservoir hypolimnion to nearer the surface. When reservoir surface waters achieved relatively warm temperatures in early summer, gate elevations were lowered slightly in order to maintain release temperatures at the target level of 13°C. Empirical data and regression models suggested that air temperature and discharge level were the primary factors that influenced downstream rates of change in water temperature. Best predictive models for water temperature had independent variables of air temperature, discharge, and discharge2 (Table 5). The F-statistics for Type III sums of squares suggested that air temperature was the most influential factor affecting water temperature predictions and increased in importance downstream of the dam. Negative 23