6025

• UCREFRP Catalog Number: 6025
• Author: Kaeding, L. R. and D. B. Osmundson.
• Title: Report on the Studies of the Endangered Fishes of the Upper Colorado River As Part of Conservation Measures for the Green Mountain and Ruedi Reservoir Water Sales
• USFW Year: 1988.
• USFW - Doc Type: Second Annual Progress Report.
• Copyright Material: NO

the lower 18-mile reach. The more upstream of the two backwaters that
yielded YOY was 0.5 miles downstream from the collection site of the larva
found in August (Fig. 3). Mean catch per effort of YOY squawfish for the
reach was 2.75/100 m2 (SD = 9.34). Mean total length of these fish was 27.0
mm (SD = 5.9; Table 5); estimated post-hatching age was 77 days (the oldest
was estimated to have hatched on 8 July).
Razorback Sucker
Because identification techniques have not yet been developed, no larval or
YOY razorback suckers have been identified in samples collected from the 15-
mile reach during 1986 or 1987. However, the Larval Fish Labortory at
Colorado State University is currently developing techniques to distinguish
among the early life stages of native sucker species. Our samples await
development of these techniques.
.Spawning of-Endangered Fishes
Colorado Squawfish
Year-round tracking studies during 1986-87 indicate that Colorado squawfish
have a relatively limited range during much of the fall-spring period. When
the spring flood waters subside and the water warms, squawfish begin to
exhibit their most extensive movements. Much of the movement between late
June and late August may represent migrations to and from spawning areas, or
movements in search of such habitats.
The estimated ages of larvae collected in fall enable us to estimate dates
of spawning activity for each year. In turn, interpretation of radio-
telemetry data is aided by our knowing when spawning occurred; this allows
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