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 Adult fish monitoring

Discussion

Among the two listed species studied, only Colorado pikeminnow adults were detected
using the Duchesne River above the direct influence of the Green River between 1997 and 1999.
Only four razorback sucker were captured downstream ofMyton between 1997 and 1999, and all
were found near the confluence of the Green River. Most razorback found in the Duchesne River
have been captured in the lower 2.5 mi of the river during the spring months (Archer et al. 1986);
however Cranney (1994) observed a single individual at rmi 11.4 in 1993. Although Cranney
(1994) provided several historic references to captures of Colorado pikeminnow in the Duchesne
River, he stated that the first record of razorback sucker in the Duchesne River was made by
Bio West, me. in a 1978 survey in the lower 0.1 rmi of the river. Our data indicated that most
razorback sucker use only the lower reach of the Duchesne River, specifically the area influenced
by water elevation of the Green River. Razorback sucker have been observed in tributary mouths
and floodplain outflows in the spring, especially following spawning in late May and June (Tyus
and Karp 1990, Modde and Irving 1998, Modde 1996). Outside of the areas influenced by the
Green River, razorback sucker do not appear to be common in tributaries of the Green River
subbasin. Razorback sucker have been reported in the Yampa River as far upstream as Lily Park
(- rmi 50.0), but few have been captured in the White River ( one by UDWR unpublished data,
and two by FWS, unpublished data) despite extensive sampling during the last decade. Following
collections oflarval razorback sucker near the mouth of the San Rafael River, Chart et al. (1999)
concluded that razorback sucker may be spawning either in the Green River near the San Rafael or
in the San Rafael itself. One possible larval razorback sucker (i.e., not conclusively identified)
was collected during this study in 1998, however extensive sampling in 1999 failed to capture any
larval razorback sucker (Brunson and Christopherson 2003). Razorback sucker were once
common in the Gunnison and San Juan tributaries of the upper Colorado River Basin and in
several larger tributaries in the lower Colorado River Basin (Minckley et al. 1991). It is likely
that ifrazorback sucker were more abundant in the Green River subbasin, fish would probably be
collected more frequently in smaller tributaries; however, because razorback sucker occupy large
river habitats, it is unlikely that the Duchesne River above the influence of the Green River would

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