9561 - Laserfiche WebLink

Home Browse Search

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Duchesne River Adult fish monitoring cited Division of Wildlife Resources stream survey records of Colorado pikeminnow in the Duchesne River above, and within our study area as early in 1956 and 1968. When the Duchesne River had higher, stable baseflows prior to physical alterations (as per CH2M Hill 1997), it is probable that Colorado pikeminnow occupied the Duchesne River in all months of the year. Failure to use the Duchsesne River during the winter base flow period may be a response to the periodic occurrence of extremely low base flows that have occurred in the last sixty years. During the low flow year of 2000, no radio-implanted Colorado pikeminnow were observed in the Duchesne River after May. m addition, the structural complexity lost in the lower river (Brink and Schmidt 1996, Geauman et al. 2003) may have reduced the useable area ofthe lower Duchesne for Colorado pikeminnow. Colorado pikeminnow in the Green River use floodplain habitat in the Green River as flood flows appear in the spring (Tyus 1986, Modde and Fuller 2002). Bioenergetically, floodplain habitats offer warmer temperatures, greater prey availability, and lower maintenance requirements (i.e., lower velocities) for large predators such as Colorado pikeminnow. The appearance of Colorado pikeminnow in the Duchesne River coincided with increased flows in the mainstem Green River. Thus, the utility of the Duchesne River to Colorado pikeminnow, may have been transformed from a historical permanent residence, such as the Yampa and White rivers, to an energetically favorable environment available during the entire summer in years of higher than average flows and at least through the peak flood flows during low flow years. Diel patterns of movement observed in both the 24 hour monitoring and stationary telemetry loggers suggested that fish move to different habitats that roughly coincide with the diurnal/nocturnal periods which are probably linked to feeding behavior (Miller and Modde 1999). However, as flows decline, as in 2000, when peak flows did not exceed 200 cfs, fish used the Duchesne River only a short period. Telemetry observations indicated that after pikeminnow left the Duchesne River, most were located within 22 miles of the Duchesne River confluence. The abundance of native adult fish observed in this study, together with an abundance of native juvenile fish reported by Brunson and Christopherson (2003) indicates an abundant prey base available in the Duchesne River for Colorado pikeminnow. Thus, use ofthe Duchesne River may represent opportunistic foraging behavior by local pikeminnow. Even though Colorado pikeminnow do not remain in the Duchesne River throughout the year, they depend on prey species that are produced in the tributary. Thus, although most Colorado pikeminnow are not present during the late fall and winter months, the ability of the 11