7400

• UCREFRP Catalog Number: 7400
• Author: Valdez, R. A.
• Title: The Endangered Fish of Cataract Canyon
• USFW Year: 1990.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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Detailed summaries of the fish captured for each of the 4 years by trip are presented in Appendix
E, Tables E-1 through E-4. These include an alphabetical list of species, and the number of larvae,
young-of-the-year, juveniles, and adults of each. The total numbers by species are given, as well as
the percentage of total catch.

4.2.1 Fish Composition In 1985

In 1985, the five most common species handled were the red shiner, channel catfish, carp, sand
shiner and fathead minnow (Table 8). Colorado squawfish were the sixth most common with 2.46% of
the catch. Red shiners made up over 52% of the catch, and were numerous to abundant in most
sheltered shoreline habitats. The relatively high number of adults and low number of YOY suggest.s that
1985 and 1986 were weak year classes for this species. This may be attributed to a near record runoff
that flushed non-natives from their protected habitats and delayed river warming in both years to
produce adverse conditions for spawning. The relatively low catch of red shiners in 1986 (Table 8)
supports this hypothesis of a weak 1985 year class. An analysis of year class strength and annual fish
abundance for several non-native and native species is presented in Section 4.2.5.

The second most abundant species in 1985 was the channel catfish. The total and relative catch
of this species increased in 1986 and then decreased through 1988. These data suggest that this
species experienced a st.rong year class in 1986 but weak year classes in 1987 and 1988 (Table 8),
opposite of what was seen for red shiners. The relatively low numbers of sand shiners and fathead
minnows in 1985 and 1986 also suggest.s that, like the red shiner, these species were adversely affected
by the high flows of 1984 and 1985. Yearly trends in abundance of carp were attributed to movement
rather than reproductive success. Seasonal differences in abundance of carp in Cataract Canyon (high
numbers in spring and early summer and low numbers in late summer) indicate movement by this
species into the region to spawn. Since large schools of carp were seen annually in late June milling
and leaping at the base of Rapid #23 (Big Drop 3), it appears that many of the carp in Cataract Canyon
immigrated seasonally from Lake Powell to spawn (See Appendix B: Species Discussions). The
numbers of fish that successfully ascended the rapids above Lake Powell were not determined.

Two species were caught in 1985 that were rather unexpected, an adult northern pike and an adult
gravid female (395 mm TL) kokanee salmon. The northern pike was captured in the middle of Cataract
Canyon (RM 206.5), Region 4; and the kokanee salmon was captured September 25, 1985 at the inflow
to Lake Powell (RM 200.4), Region 5. Since northern pike have not been introduced into Lake Powell,
their occurrence in this region was probably the result of extensive downstream movement from
impoundments located several hundred miles upstream (See Appendix B: Species Discussions). The
northern pike probably originated in one of three reservoirs in Colorado; Elk Head Reservoir (500 miles
from Cataract Canyon) in the Yampa River drainage, Taylor Park Reservoir (400 miles away) on the
Gunnison River, or Rio Blanco Reservoir (450 miles away) in the White River drainage. Kokanee salmon
were first released in Lake Powell at Kane Creek in 1963 and at Wahweap Creek in 1964 (Gustaveson
et al. 1985), although there are no reports of reproductive success (Personal communication with Glen
Davis, UDWR, December 27, 1989). Thus, the kokanee salmon captured in the inflow probably
originated in either Flaming Gorge Reservoir (400 miles away) on the Green River or from the Wayne
Aspinal Units (350 miles away) on the Gunnison River.

4.2.2 Fish Composition In 1986

The five most. common species in 1986 were the red shiner, sand shiner, channel catfish, carp and
fathead minnow (Table 8). Unlike the other 3 years, the relative abundance of the red shiner did not
overshadow the other species; in 1986, this species accounted for about 25% of the catch, whereas in
the other years, it consistently made up over half of the catch. This indicates that the species
experienced at least one poor year of reproduction, probably in 1985. The greater relative abundance
of sand shiners and fathead minnows in 1986 indicates that these species had weak year classes in
1984 and 1985, with initial recovery in 1986.

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