WSP00625

• File Number: 8240.200.10.B
• Description: UCRBRIP Annual Reports
• Basin: Colorado Mainstem
• Date: 1/12/1995
• Author: UCRBRIP
• Title: 1994 Annual Reports Package Part 1
• Water Supply Pro - Doc Type: Publication

In 1994, we caught 115 different squawfish in the Colorado River
between Westwater Canyon and Palisade including the lower 2,2 miles
of the Gunnison River, Forty-nine had been previously captured
during 1990-1993, In the Colorado River downstream of Westwater, 69
different squawfish were caught; 13 of these were captured in
previous years, Three of the recaptured squawfish in the upper river
had moved there from the lower river. In 1992 we found two other
squawfish in the upper river that had previously been marked in the
lower river. To date, no fish marked in the upper river have later
been captured in the lower river. Migrations of young adults
upstream suggests a dispersal mechanism for young raised in the
downstream nursery areas. Those that reach the upper river
apparently stay there. Presumably this is in response to the better
adult habitat located in the upper river. Analysis of scales from a
sample of young adults that have become numerous in recent years
indicated that what was previously thought to be a strong cohort, was
actually made up of fish hatched in 1985, 1986, and 1987. However,
most of the young adults apparently were hatched in 1986.

The spring runoff period ended abruptly in mid-June before the
sampling regime ended. Unlike previous years, squawfish moved to
their spawning sites during mid-June while we were still sampling.
As a result, we happened onto a previously unknown spawning site in
the middle of the Grand Valley. We captured 19 different squawfish
in a 0.3 mi reach; 16 of these were captured from one pool. This
pool was associated with a cobble bar formed at the mouth of a side
channel created during the 1993 high spring runoff period, Water
temperatures were 19.0-23.5 C. Another possible spawning site was
located by Bob Burdick on the Gunnison River just downstream of the
Redlands plunge pool; 14 squawfish were captured there during the
last week of June and the first week of July when water temperatures
were 19,5-21.0 C, A spawning site near the Colorado/Utah state-line,
identified during previous years, yielded three adult squawfish,
Downstream of Westwater Canyon two other possible spawning sites were
located; four running ripe males were caught at one site and three
were caught at another site, Water temperatures were 21-23 C. Both
sites were between Cisco Landing and Fish Ford,

VII. Recommendations: We recommend that studies such as this one be
repeated periodically in the Colorado River so that trends in
population status can be more accurately monitored. The overall
population is small, making it more vulnerable to extirpation than in
the Green River Basin where squawfish are more numerous. To
calculate a population estimate, a minimum of three years of data
collection is required; to calculate a survival rate at least four
years are required. The next four-year study should probably
commence after five years have lapsed since the end of this study. A
combination of backwater trammel netting and shoreline electrofishing
should be employed. Although netting is more productive and possibly
less harmful to the fish, some reaches do not have sufficient numbers
of backwaters to sample. In addition, years of low spring runoff
result in inadequate flooding of many backwaters in the lower river,

VIII. Project Status: This project is on track and on-going through FY 95,
The final report will be written in 1995.

2