9678

• UCREFRP Catalog Number: 9678
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Flaming Gorge Studies - Draft Consolidated Report Preliminary.
• Copyright Material: NO

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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 review).
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, 11% migrated to suspected
spawning sites, and 11% moved to other locations. Nonmigratory behavior of
tracked fish (18%) was linked with non-annual spawning or sexual immaturity.
Contact was lost with 14% of the fish, but five that were lost one year
migrated in other years. Some fish (5%) were implanted after the spawning
season. Spawning migrations began about 28 days after highest spring flows
with water temperatures of 9°C or greater. Movement of fish to known spawning
areas (N=63) averaged 140.7 km (range 32-372.8 km) in downstream (73%) and
upstream (23.8%) directions, and some fish (3.2%) moved downstream in
tributaries, then upstream in the mainstream to reach these areas. Colorado
Squawfish spawned with decreasing summer flows and increasing water
temperatures. Ripe females were captured in water temperatures averaging 23°C
(range 22-25°C, n=13), but most ripe fish were males, and their mean total
length was smaller (males==555 mm TL, N=194; females=654 mm TL, N=14). An
autumn-to-spring home range was indicated by radiotelemetry and recaptures of
tagged fish. Radiotracked and recaptured individuals spawned at the same site
more than one year, suggesting two potentially different stocks. Innate and
environmental factors influencing successful reproduction should be fully
considered in managing this endangered fish. (Preliminary Abstract).
Report 6- Response of Young Colorado Squawfish and Razorback Suckers to Water
flow and Light Intensity (Paulin et al., in review).
Movement of one-, three-, six-, and 36-week-old Colorado Squawfish
Ptvchocheilus lucius, and two-week-old razorback suckers Xvrauchen 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 Xvrauchen 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 total of 410 fish captured (68 recaptured). Razorback suckers in the
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