7056

• UCREFRP Catalog Number: 7056
• Author: Archer, D. L. and H. M. Tyus.
• Title: Yampa River Colorado Squawfish Spawning Study.
• USFW Year: 1984.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

Table 5. Spawning collections, Colorado squawfish, Green and Yampa rivers.
Number Male Female
Year River Total Ripe n TL n TL
1983 Yampa 20 19 16 594 3 687
1983 Green 13 12 11 568 1 625
1982 Green 13 7 6 509 1 640
1981 Yampa 34 31 27 535 4 734
1982 Yampa 1 1 1 547 0

Because so few females were captured, it was concluded that female
Colorado squawfish were either difficult to catch or less abundant than
males. Since females tend to be larger and older (Vanicek 1969) females
may be limited in number compared to males, because of differential
mortality.

Spawning Habitat

The locations of Colorado squawfish within the primary (RK 26, RM
16.5) and secondary (or replicate) (RK 29, RM 18.2) sites were mapped on
each contact day. (Figures 8 and 9). The behavior of these fish was
similar to that observed in 1981 (Miller et al. 1982): radiotelemetry
indicated the fish were selecting deep pools or eddies, and riffles. As
in 1981, the fish would remain in deep pools/eddies, abruptly move to
cobble bars, then return to the pools/eddies. This behavior, similar to
visual observations made for spawning northern squawfish (Beamsderfer
and Bjorn 1982), warranted the division of selected habitats into two
apparent types:

1) A resting-staging habitat in pools or large shoreline eddies
where the fish may find suitable resting and feeding habitat
between spawning forays or where males may gather around females
until they were ready to deposit eggs, and;

2) A deposition-fertilization habitat in riffles, where males
and females congregate and the females deposit eggs and the
males fertilize them.

Our data suggested that spawning Colorado squawfish selected river
reaches that had deep pools/eddies in close proximity to riffles. Also,
riffles selected for spawning were not uniform, shallow riffle areas
that ran all the way across the channel; rather, riffles used lay adjacent
to deeper runs. This would seem logical for the Colorado squawfish,
since it is a big fish. Should these observations be true, they may aid
in explaining why the Colorado squawfish selects the lower Yampa Canyon,
and especially the deep pool/riffle/pool habitat between RK 24-30 (RM
15-19) for spawning. In the upper canyon, relatively large areas are
associated with a different slope-discharge-substrate relationship, with
steep slope, high velocity and large substrates (J.S. O'Brien, Personal
Communication).

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