9561

• UCREFRP Catalog Number: 9561
• Author: Modde, T. and G. B. Haines.
• Title: Adult Fish Use in the Duchesne River Below Myton, 1997-2000.
• USFW Year: 2003.
• USFW - Doc Type: 84-3,
• Copyright Material: NO

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Duchesne River Adultfish monitoring

river to provide a prey base for pikeminnow is dependent upon prey species produced in the
Duchesne River. Many of the abundant fishes in the Duchesne River (i.e., flannelmouth sucker,
white sucker and bluehead sucker) probably represent prey for Colorado pikeminnow. m this
regard, tributaries represent important areas of prey production for Colorado pikeminnow
(Stanford 1994). Because nearly half of the pikeminnow captured were below 500 mm, tributaries
like the Duchesne River may be particularly important to young adult Colorado pikeminnow
attempting to find areas to occupy outside established home ranges oflarger pikeminnow.
Although records are not available, if a historically stable base flow regime existed in the
past, it is probable that the Duchesne River supported Colorado pikeminnow throughout the year,
as occurs in the White and Yampa rivers. The highest densities of Colorado pikeminnow in the
upper Colorado River Basin occur in the White River which has the highest average base flow of
any tributary in the basin. Conversely, the Duchesne and Price Rivers which have the lowest base
flow among the major tributaries of the Green River during have the lowest densities of
pikeminnow densities in the subbasin (McAda et al. 1998, Cavalli 1999). Colorado pikeminnow
are highly mobile fish capable of traveling long distances (Tyus 1986, Irving and Modde 2000).
Use of the Duchesne River for only a portion of the year may represent behavioral opportunism
where predators seek an available prey base as flows allow, and retreat to the Green River as base
flows decline, as was observed in the summer of2000 (flows rarely exceeded 100 cfs). Given
current water availability constraints, the Duchesne River may be managed as a spring and
summer residence by maximizing production of a prey base for local adult and subadult Colorado
pikeminnow.

Conclusions

1. Most razorback sucker using the Duchesne River are located in the lower reach of the river
(i.e., lower 0.6 rmi) influenced by the Green River, and this use seems to be confined to the spring
months immediately before and after spawning.

2. Colorado pikeminnow were found throughout the Duchesne River between the Myton Bridge
and the confluence with the Green River, although more fish were found in the lower reach
downstream of confluence with the Uintah River.

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