WSP00173

• File Number: 8240.200.10.A
• Description: UCRBRIP Habitat Restoration
• Basin: Colorado Mainstem
• Date: 10/8/1997
• Author: UCRBRIP
• Title: Final Habitat Restoration Program FY 1998 Work Plan Part 2
• Water Supply Pro - Doc Type: Publication

research.

VII.A.2. Develop interim management objectives (IMO?s)
periodically for each species and an index to population
status.

III. Study Background/Rational and Hypotheses:

The Interagency Standardized Monitoring Program (ISMP)
relies heavily on catch per unit effort (CPUE) as an index
of young-of-the-year (YOY) Colorado squawfish abundance.
However, recent work casts some doubt on how well CPUE
reflects population density. Haines et al. (1997) found only
weak correlation between estimates of CPUE and abundance
measured by capture/recapture methods. However, a longer
series of data is needed to determine the true relationship.

Overwinter survival of YOY Colorado squawfish is an
important parameter needed by the Colorado squawfish
population model developed for setting management
objectives(Crowl and Bouwes 1997). Haines et al. (1997) and
Valdez et a1. (1995) estimated overwinter survival, and they
found it usually ranged between 40 and 60 percent. Again,
however, a longer series of data is needed to determine the
year to year variation and to relate survivorship to winter
conditions.

The goals of this.study are 1) to evaluate the relationship
between CPUE sampling procedures used.by ISMP and abundance
of YOY Colorado squawfish, and 2) to obtain overwinter
survival estimates of young Colorado squawfish that can be
used in the Management Objective population model. Specific
objectives include:

1. Estimate number and CPUE of age-O Colorado squawfish
in the autumn for 20 mile river reaches of the middle
(Ouray area) and lower (Mineral Bottom area) Green
River.

2. Estimate number and CPUE of age-l Colorado squawfish
in the spring for 20 mile river reaches of the middle
(Ouray area) and lower (Mineral Bottom area) Green
River.

2