7864 - Laserfiche WebLink

Home Browse Search

Table 1. Maximum upstream and downstream movements of transmitter-implanted adult razorback sucker collected from the Green and Yampa rivers during 1993-1995. Travel was based on the maximum movement from the location the fish occupied during the second week of May each year (during 1993- 1994, starting point was capture site). 1993 1994 downstream upstream downstream upstream Frequency 40.059 19.0 25.8 93.3 33.8 40.069 60.4 29.8 99.0 34.6 40. 11 0 57.9 23.3 30.6 20.9 40.120 21.1 0 4.8 45.9 40.140 40.2 0 30.6 1.6 40.150 0 32.2 112.7 0 Average 33.1 18.5 61.8 22.8 Std dev 21.7 14.0 43.8 17.2 Two patterns of movement were observed among individual fish. Of the six surviving adults, four fish moved downstream more than 80 km after spawning at least once during the two year period. Two fish were located in the river within the boundary of the Ouray National Wildlife Refuge and two others were just upstream of the refuge during the high flow period. After these long downstream movements fish moved upstream of the Escalante spawning area within one or two months. The remaining two fish showed little movement and remained between Island Park and Split Mountain Canyon throughout the year. Movement of fish to the Escalante spawning area (RK 492-501) was associated with increases primarily in discharge and, to a lesser extent, temperature. In 1994, fish were not observed on the spawning bar when maximum daily temperature first increased to 160 C, whereas, as flows increased at the greatest rate, fish were observed on the bar despite the reduction in temperature (Figure 5). The greatest number offish found on the spawning bar (three) in 1994 was coincident with peak flows and daily maximum temperatures exceeding 140 C. In 1995, the greatest number (five) of razorback sucker in the spawning area occurred coincident with a sharp increase in discharge (approximating the magnitude observed the previous year) on the ascending limb of the hydrograph (Figure 5). Given this initial response to flow, two individuals remained at the spawning area during the peak flow period of late May and early June, 1995. Habitat use Adult razorback sucker monitored with telemetry during the spring and summer of 1993 used main channel habitat, primarily runs, eddies, or intermediate positions between eddies and runs (Le. eddy fence) (Figure 6). Most fish occupied habitat 17