7713

• UCREFRP Catalog Number: 7713
• Author: U.S. Fish and Wildlife Service, C. R. F. R. T.
• Title: Colorado Squawfish Recovery Plan.
• USFW Year: 1991.
• USFW - Doc Type: \
• Copyright Material: NO

Life History ,
Habitat Preference
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easonally variable
Colorado squawfish
are adapted to rivers with
silt loads, and turbulence. Young-of-the-year (up to 64 mm [2.5 in.] TL),
juveniles (65-200 mm [2.5-8 in.]), and subadults (200-400 mm [8-16 in.]) live
in shallow backwater areas, with little or no current over silt and sand
bottoms (Haines and Tyus 1990; Holden 1913; Holden and Stalnaker 1975a, 1975b;
Holden and Twedt 1980; Miller et al. 1982a, 1982b; Tyus and Haines 1991;
Ualdez et al. 1982b; Valdez and Wick 1983; Wick et al. 1979, 1981). There is
a change in habitat preference at about 200 mm (8 in.) TL (Miller et al.
1982a), with larger fish selecting deeper water of at least some velocity.
Adults are large-river fish, found in a variety of depths and velocities over ,
silt, sand, gravel, and boulder substrates (Holden 1973; Holden and Twedt
1980; Holden and Wick 1982; Miller et al. 1982a, 1982b; Tyus et al. 1982a,
1984; Valdez et al. 1982b; Wick et al. 1979, 1981). '
Radiotelemetry studies (Miller et al. 1983; Tyus 1985, 1986; Tyus and McAda
1984; Tyus et al. 1982b; Wick et al. 1983) have provided considerable
information on habitat usage of adult Colorado squawfish. Adults use various '
habitats depending upon season, streamflow, water temperature, and
availability (Holden and Wick 1982; Tyus and McAda 1984; Tyus 1990; Wick et
al. 1983, 1985, 1986). During peak runoff, adults move into backwater areas

or flooded riparian areas where velocity is lower and water temperatures are '
higher than in the main channel (Wick et al. 1983). During the decline in
water level following peak runoff, spawning adult fish move into run-riffle
areas and also occupy run, eddy, and pool habitats (Tyus 1990). Adult
Colorado squawfish exhibited little movement during winter (October-April) in
the upper Green River (Valdez and Masslich 1989). Of 20 adults radio-tagged
in October, 15 moved less than 5 km by the end of the following March. The '
fish occupied primarily slow runs, slackwater, eddies, and backwaters.
Temperature Preference '
The thermal tolerance of Colorado squawfish is broad, as evidenced by the
range of temperatures to which the species was presumably adapted. Summer '
water temperatures in the vicinity of Yuma, Arizona, for example, commonly
approach or exceed 35oC (95oF) and may drop to lower than lOoC (50oF) in
winter (Minckley 1979). In the Upper Basin, water temperatures generally
range from 25oC (77oF) during the summer to freezing (OoC [32oF]) in winter. '
Tyus (1990) summarized the water temperatures associated with prespawning,
migratory, and spawning periods for adult Colorado squawfish in the Upper
Green River Basin. Spawning migrations were initiated at water temperatures
of 14-20oC (57o-68oF), and spawning occurred at temperatures of 22oC (72oF)
(range 15-27.5C [59o-82oF]). In the Yampa River, migrations and spawning
periods varied between years. Migrations were initiated from May 12, to
June 10, associated with a mean water temperature of about 14oC (57oF), and
spawning occurred at 21oC (70oF) (Table 1) (Tyus and Karp 19$9). However,
Tyus et al. (1987) and Wick et al. (1985) cautioned that main channel '