9583

• UCREFRP Catalog Number: 9583
• Author: BIO/WEST Inc.
• Title: Annual Summary Report 1993 - Survival of Age-0 Colorado Squawfish in the Green and Colorado Rivers ‎(UDWR Contract No. 90-2558)‎.
• USFW Year: 1994.
• USFW - Doc Type: Logan, UT.
• Copyright Material: NO

3.1.5 1991 Year Class
A total of 186 age-0 Colorado squawfish were captured in this reach in fall 1991, resulting in a catch rate of
2.23/100 m2. By spring 1992 total numbers decreased by 63% to 69, and CPE decreased significantly (Students
't', P>0.05) by 62% to 0.84/100 m2.
Fish captured in spring 1992 averaged 43 mm TL, compared to those captured the previous fall (1991), which
averaged 40 mm TL. This resulted in an average growth of 6 mm from fall to spring.
Three juvenile squawfish, ranging in size from 161 to 169 mm TL, were captured in fall 1991. These fish were
captured together at RM 43.5.
Distribution of age-0 Colorado squawfish captured in fall 1991 and spring 1992 are presented in Figure A-12.
Age-0 squawfish were more abundant in the lower 50 miles of Reach 3 during fall 1991. The same general
trend was observed in spring 1992 sampling, indicating little or no downstream transport.
3.1.6 1992 Year Class
A total of 119 age-0 Colorado squawfish were captured in this reach in fall 1992, resulting in a catch rate of
0.82/100 mZ. By spring 1993, total numbers decreased by 26% to 88, and CPE was 1.03/100m2. Spring catch
rates were not significantly different (Students 't', P>0.05) from those reported for fall 1992 sampling.
Fish captured in spring 1993 averaged 45 mm TL, compared to those captured the previous fall (1992), which
averaged 37 mm TL. Average total length increased by 8 mm from fall to spring.
A total of 11 juvenile Colorado squawfish, ranging from 61 to 93 mm TL, were captured in fall 1992 (Table
4). This compared to 17 juveniles, ranging from 67 to 90 mm TL captured in spring 1993.
Distribution of age-0 Colorado squawfish captured in this reach in fall 1992 and spring 1993 are presented in
Figure A-13. No significant downstream transport was noted.
3.1.7 1993 Year Class
A total of 1606 age-0 Colorado squawfish were captured in this reach in fall 1993, resulting in catch rate of
5.49/100 mZ. Average length of these fish was 37 mm TL. Distribution of age-0 Colorado squawfish captured
in fall 1993 is presented in Figure A-14. Sampling will be conducted in spring 1994 to complete the
assessment of the 1993 year class.
3.1.8 Svmaatric Saecies
Age-0 Colorado squawfish represented the second or thud most common species in backwaters in the lower
Green River in fall and spring (as indicated by mean arithmetic CPE for "primary backwaters") (Figure A-15).
This illustrates that the species is having good reproductive success in this region of the upper basin, but
apparently suffers from poor survival and recruitment to adult stage.

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