7956

• UCREFRP Catalog Number: 7956
• Author: Day, K. S.
• Title: Colorado Squawfish Population Trends, Upper Green River And Lower White River, Utah, 1990-1994 ‎(Draft)‎.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: NO

backwater were searched only for squawfish, which were measured to length and
released. Numbers, and sometimes lengths, of all other native species and some
introduced species were also noted.
Physical measurements of all backwaters sampled were taken in an attempt to
determine squawfish habitat preferences. Physical measurements included surface area
(my), water depth (1/10 ft) along hauls and at the deepest point of the backwater,
substrate type and depth, and water temperature (°C).
Upon completion of data gathering at the -first 2 suitable backwaters in a 5-mile
subreach, the crew proceeded downstream to the next subreach. Sampling procedures
were repeated within this subreach as described. This process was repeated until 2
backwaters had been sampled in each subreach, or the crew reached RM 215.
.. ~,
RESULTS AND DISCUSSION
Late-juvenile/Adult Monitoring-,
A total 205 late juvenile/adult Colorado squawfish were captured during
monitoring of standardized river reaches from 1990-1994 (Table 1). This-represents a~
72% increase from the period 1986-1989 (Cranney 1990).. An additional 56 squawfish
were captured in 2 elective reaches sampled• in 1993 and 1994. Capture rates in 1990
matched the low rates reported by Cranney for 1987 and 1988 (Figure 3). They
remained low through 1992 in 3 of 4 Reaches. Mean catch-per-unit effort (CPUE;
squawfish/hr) in Reach 2 increased 5-fold in 1991, however, and remained at that level
through 1993. Capture rates in Reaches 3 and 13 doubled between 1992 and 1993.
Overall squawfish captures increased dramatically in 1994. Reaches 1, 2 and 13 had the
highest CPUE since standardized monitoring began. Although CPUE for Reach 2 did
not surpass previous highs, the number of fish captured (12) was nearly equivalent to the '
high years 1986-1988. The Elective Reach sampled in 1994 (RM 280 to RM 262) had
the highest CPUE (3.48 squawfish/hour) reported on the upper Green River since
standardized monitoring began in 1986.
The number of squawfish observed but not captured showed a corresponding
increase (Table 2). Ninety squawfish were observed but not netted, a third of these in
the White River. The ratio of fish observed to fish captured varied from 0.0 to 0.72 over
the reporting period. The averaged for the period was 0.34. Ratios were generally
highest in the White River and Ouray reaches, both between and over years.
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