7046 ‎(3)‎

• UCREFRP Catalog Number: 7046
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Final Report\
• USFW Year: 1992.
• Copyright Material: NO

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Gill and trammel nets were used primarily to sample larger fish in deep habitats such as pools,
run and eddies, Information documented for each netting effort included location, temperature,
primary and secondary habitat, and duration of net set.

ElectroflShing was conducted in all habitats and reaches of the study area. Two types of
electrofishing boats were used. 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 WP-15 control
unit; and a Jon boat equipped with a 3500-watt generator and a Coffelt WP-15 control unit, The
canoe was used to electroflSh areas where the Jon boat could not be used either because of low water
or inadequate launch access for a larger boat. The canoe was controlled by one paddler in the stem,
while fish were netted by one person kneeling in the bow of the boat The Jon boat was powered
by a 25-hp Mercury motor, and one or two persons netted fish from a standing position in the bow
of the boat, Electrofishing was generally conducted along shorelines, however low flows often
necessitated shocking in midchannel. Catch rates for electroflShing were computed as number of fish
captured per 10 hours of electrofishing (current-on) for each type of boat.

3.3 Habitat Analysis

Physical, chemical and biological attributes of the Dolores River were assessed to determine
habitat suitability of the system for Colorado squawfish. Since little was known about historical or
present use of the Dolores River by Colorado squawfish, determinations of habitat suitability were
based on data collected from occupied habitat in other Upper Basin drainages, A majority of this
information was assimilated and summarized as habitat suitability index (HSI) curves by Valdez et al.
(1987). These HSI curves were used as the primary criteria for judging the suitability of physical
habitat in the Dolores River. Observations by other researchers including Miller et al. (1982),
Lamarra et al, (1985), Archer and Tyus (1984) and Wick et al. (1983) were also considered for
determining habitat suitability.

Physical habitat attnbutes that were evaluated in the Dolores River during the study included
flow, velocity, temperature, depth, substrate and habitat structure and complexity. These physical
attributes were evaluated using four techniques including: 1) an ocular habitat survey of the entire
study reach, with periodic spot measurements of depth and substrate; 2) review of U.S, Geological
Survey (USGS) flow data; 3) systematic cross-sectional characterizations within the six reaches and;
4) detailed measurements of physical habitat at specific locales determined to represent important
habitat components, i.e. potential spawning and nursery areas.

Chemical attributes of the Dolores River were assessed by collecting and analyzing water quality
at six sample sites (Figure 2). Criteria used to determine the suitability of chemical factors with
regards to Colorado squawfish were based on EP A water quality standards for aquatic life (EP A
1986). Additional information on the influence of water quality parameters on Colorado squawfish
was assimilated from literature where possible.

Biological attributes of the Dolores River used to evaluate the suitability of the system for
Colorado squawfish included: 1) food base, including benthic macroinvertebrate and fish composition;
and 2) composition and abundance of sympatric fish species, including potential competitors and
predators. Overall suitability of the Dolores River as an integration of physical, chemical and
biological attributes was also addressed.