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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Samples were preserved in 70% ethanol and transported to BIO/WEST laboratories for processing
and analysis.

4.0 RESULTS

4.1 Summary of Fish Collections

A total of 14 species of fish representing 5 families were captured in the Dolores River in 1990
(Table 4). This list is similar to that reported by Holden and Stalnaker (1975) and Valdez et al.
(1982) except that black bullhead and bluegill were not reported in 1975 and bluegill were not
reported in 1982. White sucker (Catostomus commersoni), rainbow trout (Oncorhynchus mvkiss) and
brown trout (Salmo trutta) were report by Valdez et al. (1982) but were not captured in 1990.

Table 5 presents a summary of fish species captured in 1990 by trip and total for the year. Table 6
presents a summary of life stages captured for each species in 1990. As percentage of total catch,
the most common species of fish captured in 1990 were red shiner (37.5), fathead minnow (23.6) and
sand shiner (22.7). These three non-native fish comprised 83.8% of the catch. Of the 14 species
reported, 10 are non-native and 4 are native or endemic to the Colorado River system (Tyus et aI.
1982). Native species comprised 13% of the total catch including flannelmouth sucker (7.0), roundtail
chub (3.0), bluehead sucker (1.5) and speckled dace (1.5). No endangered species (Colorado
squawfish, bonytail, humpback chub or razorback sucker) were captured in the Dolores River in 1990.

Native species as a percentage of the total species captured by electrofishing and netting for each of
the subreaches are presented in Figure 3. Increases in percentage composition of flannelmouth
sucker and roundtail chub in higher subreaches of the study area suggest that these species may be
more prevalent in the upstream reaches. Percentage composition of bluehead suckers and specked
dace remains relatively constant throughout the study area Small sample size in Reach 4 precludes
interpretation of results. Figure 4 presents percentage composition of catch for native species versus
non-natives. Strong trends are apparent indicating that native species were more prevalent in the
upper portion of the study area

Figure 5 presents native species as a percentage of total catch for seining in the Dolores River.
These data also indicate that natives were more prevalent in the upper portions of the study area
Figure 6 presents composition of natives versus non-natives.

4.2 Summary of Fish Collections by Gear Type with CPE Statistics

A summary of all fish sampling efforts by gear type is presented in Table 2. An attempt was made
to expend similar effort during each of the 3 sampling trips for electrofishing, gill and trammel nets,
and seining. Variation in effort is reflective of variable conditions present during each sampling trip.
Also, time spent conducting reconnaissance and habitat assessment during Trip 1 reduced time
available for sampling. Summaries of fish species collected by life stage and CPE for each of the
principal gear types are presented in Tables 7-12.

4.2.1 EIectrofishing

The highest catch rates for the electrofishing canoe (Table 7), were for flannelmouth sucker (121.0
fish/l0 hours), roundtail chub (11 0.1), carp (47.1) and bluehead sucker (37.8). The highest catch rates

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