7729

• UCREFRP Catalog Number: 7729
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Annual Summary Report - 1990\
• USFW Year: 1991.
• Copyright Material: NO

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Electrofishing was conducted in all habitats and subreaches of the study area Two types of
electrofishing boats were used in 1990. These included a 17 foot ABS plastic canoe, equipped with
either a 2500-watt generator and a Coffelt 2C control unit or a 3500-watt generator and a VVP-15
control unit. A Jon boat was also used with a 3500~watt generator and a Coffelt VVP-15 control
unit. The canoe was used to electrofish shallow areas with little flow. It was controlled by one
paddler in the stem, while fish were netted by a second person kneeling in the bow of the boat. The
Jon boat was used in deeper water with higher flow. It was powered by a 25 hp Mercury outboard
motor, and two persons netted fish from the bow of the boat. Catch rates for electrofishing were
computed as number of fish captured per 10 hours of electrofishing (current on) for each type of
boat.

3.3 Habitat Analysis

In order to address Objective 2 of the study, physical, chemical and biological attnbutes of the
Dolores River were assessed to determine habitat suitability for Colorado squawfish. Since little is
known about historical and present use of the Dolores River by Colorado squawfish, suitability of
habitat was determined on the basis of data collected from occupied habitat in other Upper Basin
drainages. Consequently, criteria used to evaluate the suitability of habitat in the Dolores River were
based on data collected for Colorado squawfish from the Yampa, Green and Colorado Rivers. A
majority of this information has been assimilated and summarized as habitat suitability curves by
Valdez et. at. (1987). Additionally, observations by other researchers including Miller et at. (1983),
Lamarra et at. (1985), Archer and Tyus (1984) and Wick et al. (1983) were also used as a basis for
determining habitat suitability.

Physical habitat attnbutes evaluated in the Dolores River in 1990 include; flow, velocities,
temperature, depth, substrate and habitat structure, and availability. These physical attributes were
evaluated using three techniques including: 1) a visual habitat survey of the entire study reach with
periodic spot measurements of depth and substrate; 2) review of USGS flow data; and 3) detailed
measurements of physical habitat at specific locales determined to represent important habitat
components, i.e. potential spawning and nursery areas.

Chemical attnbutes of the Dolores River were assessed by collecting and analyzing water quality
samples at various locations within the study area. Criteria used to determine the suitability of
chemical factors with regards to Colorado squawfish is based on EP A water quality standards for
aquatic life (EP A 1986). Additionally, information on the influence of water quality parameters on
Colorado squawfish was assimilated from literature.

Biological attnbutes of the Dolores River evaluated in 1990 include: 1) food base including benthic
invertebrate and fish composition; 2) composition and abundance of competitive fish species and; 3)
composition and abundance of predatory fish species. Overall suitability of the Dolores River was
determined by the integration of physical, chemical and biological attributes and is addressed in the
results section.

Habitat analysis performed during 1990 included both qualitative and quantitative approaches.
Qualitative habitat analysis involved a general reconnaissance of the entire study reach. The
objectives of this generalized qualitative survey were to: 1) determine the variety of habitats that exist
within the study area; 2) determine whether significant physical changes have occurred in the Dolores
River drainage since the USFWS survey in 1981-82, i.e. presence of barriers to movement,

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