7864

• UCREFRP Catalog Number: 7864
• Author: Modde, T. and E. J. Wick.
• Title: Investigations Of Razorback Sucker Distribution, Movements And Habitats Used During Spring In The Green River, Utah.
• USFW Year: 1997.
• USFW - Doc Type: Recovery Program Project No. 49,
• Copyright Material: NO

associated with foraging behavior. During the spring and summer of 1995, 12 adult
razorback sucker were collected in a wetland on the Ouray National Wildlife Refuge
(Modde 1996; USFWS unpublished data). Fish presumably accessed the wetland
during the peak spring flows when the wetland was connected to the river, and
remained in the wetland after the river elevation receded. Razorback sucker have also
been observed in floodplain wetlands by Tyus and "Karp (1990) and Bruce Waddell
(U.S. Fish and Wildlife Service, unpublished data). In 1993, three fish monitored by
telemetry were located at the mouth of a tributary (Ashley Creek) following spawning.
Two razorback sucker traveled downstream to the vicinity of the Ouray wetland complex
during both years of the study. Historically, floodplain habitat along the Green River
between the Yampa and White rivers was inundated during the spring months
(approximately 20,000 cfs or 566 m3/s) an average of 2 out of every 3 years (U.S.G.S.
records from the gage at Jensen, Utah). As suggested by Tyus and Karp (1990),
razorback sucker attraction to wetland outlets and tributary mouths may be related to
temperature preference (Bulkley and Pimentel 1983) and productivity (Mabey 1993).
Fish implanted with radio transmitters returned upstream to the vicinity of Split Mountain
Canyon at the onset of the base flows.

Cueing to natural hydrographic and thermal regimes in riverine environments
may effectively concentrate fish at spawning sites, thus increasing the efficiency of
successful spawning, particularly within small populations. Razorback sucker in Lake
Mohave, Arizona, in the absence of riverine cues, spawned over a longer period of time
between November and May (Minckley 1983) with most of the individuals spawning
over a shorter period of time. Despite chronological differences, temperature reported
for peak razorback spawning in the lower basin, 100 and 150C (Bozek et al. 1984), was
somewhat lower but similar for razorback sucker in the upper Colorado River basin
(Tyus 1987; Tyus and Karp 1990). Thus, discharge cues are hot needed for
reproduction, but flow patterns can initiate movement that may help synchronize
spawning adults on historic spawning sites. The latter is important in maximizing
reproductive success in small populations. The timing of reproduction is also important
if floodplain inundation is necessary to optimize survival of early life stages of razorback
sucker (Tyus and Karp 1990; Modde et al. 1996).

Tyus and Karp (1990) identified the Yampa River and Escalante (Jensen)
spawning areas, and Tyus (1987) suggested that spawning may also occur near the
mouth of the Duchesne River and in Island Park in Dinosaur National Monument.
Telemetry data supported the concept that multiple spawning sites existed, including
the Yampa River near its confluence with the Green River, the Escalante spawning
area, and possibly the lower portion of Island Park. Transmitter-implanted razorback
sucker moved to the vicinity of the Duchesne River either prior to or following spawning.
However, capture data showed that some razorback sucker occupied the Duchesne
River area during the peak spawning period. Tyus and Karp (1990) suggested that
razorback sucker showed fidelity to the Escalante spawning area. They observed a
razorback sucker, via telemetry, bypass the Escalante spawning area enroute to the
Yampa River site. However, fidelity to spawning sites is difficult to ascertain from

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