7603

• UCREFRP Catalog Number: 7603
• Author: Nesler, T. P.
• Title: Endangered Fishes Investigations
• USFW Year: 1991.
• USFW - Doc Type: Federal Aid Project #SE-3 - Job Progress Report.
• Copyright Material: NO

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results of each years' sampling is analyzed and reported annually by FWS.
Data from these files were subsequently used in data analyses for Jobs 1 and 2
above.

Job 7:

Management Strategy for Exotic Fishes Affects on Endangered Fishes

This issue paper was developed in two parts. First, a summary review was
conducted of the existing literature dealing with nonnative fish species
within the Colorado River Basin, and included relevant species literature from
outside the Basin. Secondly, management recommendations were gathered via the
Delphi technique (Zuboy 1981), using a questionnaire to acquire expert opinion
from biologists and researchers with experience concerning Colorado River
Basin endangered fishes. An overall strategy would be based on a synthesis of
the literature review and recommendations of the biologists. The elements of
the strategy may be prioritized according to the perceptions of the biologists
and from conclusions derived from the literature review.

Job 8: Colorado squawfish age and growth

Data relevant to age and growth analyses of Colorado squawfish include
length, weight, sex, date and location of capture, tag number, and a scale
sample for each capture and recapture of an individual fish. Capture,
tagging, and measuring of Colorado squawfish has been an ongoing process in
the Upper Colorado River Basin conducted by numerous researchers from various
government and private agencies since the late 1970's. Scale samples from
these fish, however, have not been standard procedure. Samples of other bony
structures for age validation, available only through killing the specimen,
are relatively few in number. The organization of capture information for the
endangered Colorado River fishes into the centralized RARE data base managed
by USFWS in Grand Junction is a retroactive process that is not complete. As
such, it was necessary to compile available Colorado squawfish capture data
and scale samples from all possible sources. This included the computerized
USFWS data base in Grand Junction as well as numerous published and
unpublished reports from Colorado Division of Wildlife, Utah Division of
Wildlife Resources, New Mexico Game and Fish Department, U.S. Fish and
Wildlife Service, Bureau of Reclamation, CSU Larval Fish Lab, Utah State
University, University of New Mexico, and BioWest Consultants, Inc.

Scale samples from 526 Colorado squawfish were available for examination.
Two hundred of these consisted of scale impressions from Green River
collections used in the age-growth study by Musker (1981). The original scale
samples from the Green River specimens were discarded, thus the analyses may
be influenced by the quality of the acetate impressions. The remaining scale
samples were collected by John Hawkins and Ed Wick during 1978-1989. This
scale collection includes fish from the Colorado, White, Gunnison, and Yampa
rivers, but is dominated by specimens from the Yampa. Only 29 Colorado
squawfish specimens were available for obtaining and analyzing other bony
structures for age estimation and scale age validation. Scale and bony
structure samples were cleaned and mounted according to standard procedures.
Age estimation and back-calculation of growth, length frequency distribution