7823

• UCREFRP Catalog Number: 7823
• Author: Miller, W. H., et al.
• Title: Colorado River Fishery Project, Part II, Final Report, Field Investigations.
• USFW Year: 1982.
• USFW - Doc Type: \
• Copyright Material: NO

bonytail chub (Gila ele ans) was listed as endangered (USFWS, 1980) and
the razorback sucker Xyrauchen texanus) was proposed for listing as
threatened; they have been included as target species. •
In order to evaluate the status, life history, and habitat require-
ments for the four target species it was necessary to characterize
fishery habitat (including physicochemical and biological parameters) so
that the function and interactions of the endangered fish could be
investigated from an ecosystem approach. Also, certain life history
information about these endangered species was needed. The Vernal field
station, therefore, organized its study with two main objectives:
1. To characterize fishery habitat. This included collections
of physicochemical data for all fish species in identified
habitats. Habitat preferences and species interactions for
all species was the desired end product. A standardized sampling
program was designed to meet this general objective.
2. To obtain life history information for rare and endangered
fish species. As stated in the MOU, specific information about
young and adult habitat requirements, migration and movement,
interspecific competition, etc., was desired. A special investi-
gations program was developed to meet this objective, and a series
of separate studies was included in the program. These individual
studies included:
a. Abundance and distribution of young Colorado squawfish.
b. Movements and habitat preferences of young Colorado squawfish.
c. Radiotelemetry of adult Colorado squawfish.
d. Habitat preference and taxonomy of Gila spp.
METHODS
Standardized Sampling Program
The standardized program was designed for sampling about 300 miles
(480 kilometers) of the Green River in 1979 to 1981: from Turks Head
at river mile RM 22 (kilometer 35) to Split Mountan, RM 320 (kilometer
515). Since it was impossible to adequately sample this entire riverine
area with allocated manpower, a sampling program was developed.
The river system consists of several 30- to 70-mile (48- to
113-kilometer) sections of relatively homogeneous fishery habitat,
including high-gradient canyons, low-gradient braided sections, and
transition zones between these two main types. The development of the
sampling design incorporated treatment of these homogeneous sections as
discrete strata (Figure 2) in order to provide a good distribution of
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