7154

• UCREFRP Catalog Number: 7154
• Author: Holden, P. B.
• Title: Habitat Requirements of Juvenile Colorado River Squawfish.
• USFW Year: 1977.
• USFW - Doc Type: FWS/OBS-77/65,
• Copyright Material: NO

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squawfish used backwaters almost exclusively in the Colorado River near

Grand Junction, although times of capture were not noted.

Small humpback chubs have similar habitat preferences to small

squawfi sh but use more of a variety of areas, especially eddies . No

previous study has reported on preferred habitats of small humpback
chubs.

Habitat preferences of adult humpback chubs have generally included

,

\ eddies near fast current (Holden and Stalnaker, 1975) and/or depths of
20+ feet (Kidd, 1977). The data collected during the present study show

no distinct preference for either depth or velocity, although some hump-

backs were caught in very fast currents (2.5 fps) and in very deep areas

(20 ft.).

Concerning electivity curves, the Cooperative Instream Flow Service

Group has set guidelines for evaluating reliability based on number of
fish captured. They suggest the following reliability levels: excellent,

200 individual measurements; good, 50-200 samples; and fair, less than

50 measurements. Using these criteria, none of the curves shown above

can be rated excellent, young-of-the-year squawfish and humpback chubs
are good, and the others only fair. The additional information from the
literature would probably increase the reliability of the young-of-the-
year squawfish data, but would add little reliability to the other groups.

It is doubtful that a two-month study of rare Colorado Basin fishes

can produce sufficient data for excellent reliability, except for young-

of-the-year fish. The endangered status of the Colorado squawfish and

humpback chub suggest extreme rareness, as, in fact, they are, Several