7180 - Laserfiche WebLink

Home Browse Search

size from 522 to 810 mm TL had been implanted. Movement patterns of these fish were somewhat different than those observed in the Green River in 1980 and 1981; with larger fish moving into or remaining in whitewater canyon areas after the spawning season. In addition, radio- tagged fish lead us to a previously suspected spawning site in Gray Canyon (Figure 1). Collections of ripe fish in Gray Canyon and subsequent young-of-the-year studies rovide the first ocumen a ion of this otentia s awnin site. One 810 mm fis o. 1 moved about 322 miles during the study period. Colorado squawfish implanted in the Green and White rivers apparently used the lower Yampa and Gray canyons for spawning in 1982. The movement patterns of radiotelemetered Green River fish are shown in Figure 6. During the 1982 (July-August) spawning season the Vernal Station sampled Yampa Canyon, on the Yampa River and in Split Mountain Canyon and Gray Canyon on the Green River for spawning Colorado squawfish. Seven ripe Colorado squawfish were collected in the vicinity of radio- tagged fish in Gray Canyon between July 13 and July 22. Only one collecting trip was made to the lower Yampa River where one ripe fish was collected. The reason for the comparative absence of ripe fish in the Yampa was provided by co-workers during a Yampa River fish study (Stoneburner, 1983), which indicated that spawning occurred about 3 to 4 weeks later than our sampling in 1982 (also 3 to 4 weeks later than spawning in 1981). Study results indicated that spawning occurred in Gray Canyon about 3 weeks earlier than spawning in Yampa Canyon. In addition to this FWS study, we also assisted Utah DWR personnel in tracking four White River fish which moved into the Green River in 1982. Movement of these fish is shown in Figure 7. Larval and Young-of-the-Year (YOY) Surveys Larval sampling in the Colorado River was initiated in mid-July and performed on a weekly basis between Palisade and the Westwater Ranger Station through August. Two sampling trips were made during August in the river reach between Westwater Canyon and Potash, Utah. An attempt was made to sample below Potash in late August; however, this effort was canceled because of equipment failure. Sampling was also accomplished in upper Lake Powell in July concurrent with radio-tracking work. Larval Color o s u fi sh (total of 148 individuals) were found throughout the Col stud a (Figure 8). Colorado squawfish arvae in ividuals) were most frequently encountered and were in highest relative abundance in samples taken from the river reach below Westwater Canyon (Westwater Canyon itself was not sampled). Colorado squawfish larvae were first collected from the river reach above Loma, Colorado later in the season than from the downstream river reach; this might reflect marked differences in the spawning time between river reaches. In the Green and Yampa rivers, 98 larval, Colorado squawfish were confirmed an a o en is ted from larva seine samples a en at the five sample stations (Table 3). These larvae ranged in size from 9.3 to 22.0 mm TL. No larvae were found in the Green River above the mouth of the Yampa River (RM 345), indicating that no reproduction - 13 -