9685

• UCREFRP Catalog Number: 9685
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1989.
• USFW - Doc Type: Flaming Gorge Studies - 2nd Preliminary Draft.
• Copyright Material: NO

Flow fluctuations in the winter may affect preferred winter habitats, and
movement patterns suggested that such fluctuations resulted in greater
movement of Colorado squawfish than in more stable conditions (Valdez and
Masslich 1989, Wick and Hawkins 1989). Fluctuation in river level greater than
5cm/h caused 190% more movement in adult Colorado squawfish in the Green River
120m downstream of Flaming Gorge Dam (Valdez and Masslich 1989).
in spring and early summer, adult Colorado squawfish were most often
located in inundated shorelines, including backwaters or bottomlands (Tyus, in
review). Radiotracking data indicated use of shoreline backwater habitat in
the 1981 low-flow year and use of flooded bottomlands during the 1983 high-
flow year (Tyus and Karp 19$9). Flooded shorelines were a7 so used by adult
Colorado squawfish during the two high-flow years, 1983 and 1984 (Tyus et al.
1987), and use of inundated portions of Old Charley Wa h was noted from late
April to May, 1985 and 1987, at flows of 226.4 - 283 m~/s. Wick et ai. (1983)
noted that in 1982 (an average-flow year), adult Colorado squawfish used
flooded shoreline areas in spring but moved to backwater habitats as the river
level dropped.
Adult Colorado squawfish occupied a variety of habitats in mid-to-late
summer, but were most common in eddies, pools, runs, and shoreline backwaters,
over sand and silt substrates (Tyus et al. 1984, 1987). Visual observations
of fish in shallow water indicated that adults used sheltered microhabitats
behind boulders, flooded vegetation, or other cover. During the summer,
radio-tagged fish were most often located in deeper shoreline habitats where
movements suggested heavy use of eddy-run interface (Tyus et al. 1987).
Capture of introduced northern pike fsox lucius and channel catfish
Ictalurus unc~tatu~ in habitats shared by adult Colorado squawfish (Wick et
al. 1985; Tyus and Beard 1990) suggests a potential-for competition and/or
predation during times of resource limitation. Although Pimenta7 et al. (1985)
found that Colorado squawfish did not prefer channel catfish as prey,
observations of channel catfish lodged in throats of adult Colorado squawfish
(McAda 1983, Pimental et al. 1985, Wick et a7. 1985) indicates that these
introduced fish are eaten by Colorado squawfish, and may cause mortality.
Conditions favorable for non-native fishes that may compete with (or other
adverse interactions) Colorado squawfish should be avoided. Species of concern
include channel catfish, northern pike, and walleye Stizostedion vitreum.
Reproduction
The initiation of spawning migration is an important component of the
reproductive cycle of the Colorado squawfish. Based on radiotracking data
(Wick et al. 1983; Tyus and McAda 1984; Tyus 1985, in review), fish in both,,.,
Green and Yampa rivers initiated spawning migrations around the Summer
Solstice; Green River fish initiated migrations about June 21 (range: May 23
to July 27) and Yampa River fish migrated about June 19 (range: May 27-July
12; Figure 4). These migrations included downstream movements in the Yampa and
White rivers and upstream and downstream movements in the Green River (Tyus et
al. 1987; Tyus, in review). Flows and water temperatures .were highly variable
within each migration period and among years. However, spawning migrations
were initiated earlier in low-water years (e.g., 1981) and later in higher:;
water years, e.g., 1983. Spawning migrations of radio-tagged Colorado.-:
squawfish were associated with highest spring flows and river temperatures
generally exceeding 14 °C (range: 14-22°C in the Green River from May 23-July
27; Tyus, in review).
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