9685

• UCREFRP Catalog Number: 9685
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1989.
• USFW - Doc Type: Flaming Gorge Studies - 2nd Preliminary Draft.
• Copyright Material: NO

Study 3: Spring-Early Summer Flow Requirements of Colorado Squawfish,
Razorback sucker, and Humpback chub.
Report 5- Potamodromy and Reproduction of Colorado Squawfish in the Green
River Basin, Colorado and Utah (Tyus, in reviewj.
Migrations and movements of Colorado squawfish Ptvchocheilus lucius were
studied by radiotracking and recaptures of tagged fish in the Green River
basin of Colorado and Utah, 1980-1988. Of 153 fish tracked, 63% were highly
mobile: 41% migrated to known spawning sites, li% migrated to suspected
spawning sites, and 11% moved to other locations. Nonmigratory behavior in 18%
of tracked fish was linked with non-annual spawning and sexual immaturity.
Contact was lost with 19% of the fish, but five that were lost one year
migrated in other years. ~~fia_~~igrations were associated with long days,
high spring flows, and increasing eir al~res. Fish tracked to known
spawning areas {n=63) averaged 140.7 km {range 32-372.8 km) in downstream
(73%), upstream {23.8%), and down- and upstream (3.2%) directions. Colorado
squawfish spawning was associated with decreasing water flows and increasing
water temperatures following spring runoff. Ripe females were captured in
water temperatures averaging 23°C (range 22-25°C, n=13). Spawning ,fish were
predominantly ripe males (male:female ratio of 13.9:1) and they were smaller
in average total length than ripe females {males=555 mm, n=194; females=654
mm, n=14). Fidelity to a specific spawning area was exhibited by 12
individuals that used the same site more than one year. Two stocks of Colorado
squawfish were separated by separate migrations to two different spawning
grounds. Genetic and environmental factors influencing successful reproduction
shou]d be fully considered in developing recovery options for this endangered
fish (Preliminary Abstract).
Report 6- Response of Young Colorado Squawfish and Razorback Suckers to Water
flow and Light Intensity (Pau]in et al., in review).
Movement of one-~, three-, six-, and 36-week-old Colorado squawfish
Ptvchocheilus lucius, and two-week-old razorback suckers Xyrauchen texanus
were evaluated in response to three water flow rates and two light levels.
Fish were placed in the center of a seven-chamber~d ~ank and their locations
recorded at water flow-rates of 0, 27, and 237 cm s- Tank hydraulics
represented natural riverine conditions: a meandering mainstream and
associated quiet (backwater) areas. The extent and direction of fish movement
was related to flow rate, time of day and fish age; downstream movement
(drift) was associated with darkness and fast flow for all ages and both..
species of fish. Similar patterns of drift have been observed in these species
in natural systems, and presumably serve to transport- young fish to productive
nursery areas. Downstream dispersal is an important species attribute of these
rare and endangered fishes {Preliminary Abstract).
Report 7- Population Size and Status of the Razorback Sucker in the Green
River basin, Utah and Colorado (Lanigan and Tyus 1989)
The status of the razorback sucker Xyrauchen texanus in the Green River,.
Utah, was evaluated with capture-recapture data collected from 1980 to 1988.
The razorback sucker population in the upper Green River (river kilometers
282-555) was estimated at 948 fish (95% confidence interval, 758-1,138), based
on a tots] of 410 fish captured (68 recaptured). Razorback suckers in the
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