7047

• UCREFRP Catalog Number: 7047
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes in the Green River, Utah
• USFW Year: 1991.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

Razorback suckers in breeding condition were captured primarily on
several cobble/gravel/sand bars in the lower Yampa and upper Green rivers
(including Echo Park and the reach from Ashley Creek to near the lower
boundary of DNM), but were also collected in flooded shorelines, bottomlands,
and tributary mouths (including Old Charley Wash, lower Ashley Creek and
Duchesne River, Stewart Lake Drain; Tyus and Karp 1990). From 1987 to 1989
(low and moderate water years), most ripe fish (98%, n=191) were collected in
flowing water in riffles, but during the high water of 1986, 30% of all ripe
or tuberculate razorback suckers were captured in flooded river bottoms of Old
Charley Wash and Stewart Lake Drain. Twelve ripe adults were observed in Old
Charley Wash in late May-early June 1986 at flows of about 537.7 - 566 m3/s
(Tyus and Karp 1990). These fish were robust and presumed in good
physiological condition due to abundant food in the inundated lowland.
Spawning of razorback suckers occurred during ascending and highest
spring peak flows, as indicated by capture of ripe fish (Figure 8; Tyus and
Karp 1989, 1990). Ripe fish were captured at water temperatures averaging
about 14-15°C (Tyus 1987; Tyus and Karp 1990). However, temperatures in
flooded areas (Old Charley Wash and Stewart Lake Drain) in spring 1986 when
ripe razorback suckers were present averaged 19.6°C (range 17.5-21°C). Main
channel temperatures were colder (mean= 15.6°C, range: 15-16.5°C) at this time
which suggests that razorback suckers may be seeking warmer habitats in the
spring. Bulkley and Pimentel (1983) reported that razorback suckers preferred
temperatures of about 22-25°C and avoided temperatures of 8-15°C. Mean monthly
temperatures were reduced at Jensen by operation of Flaming Gorge Dam (G.
Smith, pers. comm.), and current flow and temperature regimens may adversely
affect hatchability of razorback sucker eggs in the upper Green River.
Razorback sucker eggs taken in the Green River experienced poor hatching at
11°C due to fungus, but hatching was successful (90%) when incubated at 20°C
(FWS, unpublished data . Marsh (1985) noted optimal hatch in razorback sucker
larvae incubated at 20 C.
Razorback suckers exhibited both local and long-distance spring and
summer movements (Tyus 1987; Tyus and Karp 1990). Two spawning migrations
have been detected with fish movement between lower Yampa and upper Green
(below boundary DNM) rivers, and movement between upper Green River and Ouray
area (Old Charley Wash and lower Duchesne River, Tyus and Karp 1990).
Blockage of stream passage would interrupt spawning movements of razorback
sucker in the Green River basin. There is some indication that some razorback
suckers exhibit a spawning fidelity to a specific riffle (Tyus and Karp 1990)
and the importance of this phenomenon needs further evaluation, particularly
in reintroduction efforts.
The capture and artificial spawning of ripe razorback suckers in the
lower Yampa and upper Green rivers (Severson et al. 1990) and the tentative
identification of larvae in upper Green River seine collections (R. T. Muth
and D. Snyder, personal communication) suggests that razorback suckers
reproduce successfully in the upper Green River basin. However, there is
little indication of recruitment to the juvenile stage throughout the Colorado
River basin (Holden 1978; McAda and Wydowski 1980; Minckley 1983; Tyus 1987;
Marsh and Minckley 1989; Tyus and Karp 1990). Standing crops of razorback
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