8185

• UCREFRP Catalog Number: 8185
• Author: Valdez, R. A. and B. R. Cowdell.
• Title: Annual Summary Report-1992\
• USFW Year: 1993.
• Copyright Material: NO

2.0 METHODOLOGY

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Sampling included three standard sampling reaches, two on the Green River and one on the Colorado River
(Figure 1). These included Reach 4 on the upper Green River (RM 320 to RM 215); Reach 3 on the lower
Green River (RM 120 to RM 0); and Reach 1 on the Lower Colorado River (RM 120 to RM 0). This report
presents results from sampling of Reach 3. Brief sampling summaries are included from Reach 1 and Reach
4, primarily for purposes of comparisons. Analyses of overwinter survival for Colorado River Reach 1,
including catch rates of sympatric species and catch rates and numbers of Colorado squawfish are being
conducted by the U.S. Fish and Wildlife Service (Service), Grand Junction CRFP Field Station.

UTAH

WYOMING

COLORADO

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Figure 1.

River reaches sampled during post-larval, age-O Colorado squawfish monitoring.

Age-O Colorado squawfish were sampled in fall and the following spring to assess changes in density for the
year class. Fall sampling was conducted in late September to maximize catch of age-O fish large enough to
identify afield, at a time when most of these fish were aggregated in relatively warmer backwaters. Spring
sampling was in late March and early April, when water temperatures were warming and prior to onset of
spring runoff, which inundated the backwaters. Sampling was conducted jointly with UDWR and the Service.
Table 1 is a summary of trip schedules for age-O squawfish sampling of the Colorado and Green Rivers, 1987-
1992.

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