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

Reproduction and Migration
In the wild, male Colorado squawfish do not mature until they reach or exceed
400 mm (15.7 in.) TL and (based on scale ageing techniques) attain an age of
at least 6 years; females mature a year later (Seethaler 1978). Tyus (1990)
found that ripe males averaged 555 mm (21 in.) TL (n=194), but ripe females
averaged 654 mm (26 in.) TL (n=14) on spawning grounds in the Green River
basin. Hatchery-reared males matured at 5 years and females at 6 years of age
(Hamman 1981)._ Some of these hatchery fish matured naturally while others
produced gametes only after an injection of carp pituitary extract (Hamman
1981).
Colorado squawfish gonads ripen during spring runoff (May-June). Laboratory
and field studies indicate that spawning begins when water temperatures reach
about 21oC (70oF) (Hamman 1981; Miller et al. 1982a; Toney 1974; Vanicek and
Kramer 1969). Archer et al. (1985), Haynes et al. (1984), and Tyus (1990)
found that spawning occurred between late June and mid-August when water
temperature reached 18-25oC (64o-77oF), with peak spawning activity occurring
between 22-25oC. Although turbidity has precluded direct observation of
spawning behavior, radiotracking and collection data suggest similarities to
the northern squawfish (Beamesderfer and Congleton 1981; Patten and Rodman
1969).
Radiotelemetry studies and collections of spawning fish have added to the
knowledge of Colorado squawfish spawning activities, seasonal movements, and
habitat use (Miller et al. 1984; Radant et al. 1983; Tyus and McAda 1984; Tyus
et al. 1982b; Tyus 1990; Wick et al. 1983). During the spawning season, adult
Colorado squawfish have been known to migrate up to 320 km (200 miles),
upstream or downstream, to reach spawning areas in the Green River Basin
(Miller et al. 1983; Tyus 1985; Tyus 1990). Homing behavior and fidelity to
spawning locations has been indicated for Colorado squawfish in the Green and
Yampa Rivers (Tyus 1985; Tyus 1990; Wick et al. 1986). Some authors suggest
that repeated use of the same spawning areas may reflect a limited
availability of spawning habitats rather than true homing (Archer et al. 1985;
O'Brien 1984); however, Tyus (1990) reported that migrating Colorado squawfish
pass through many miles of potential spawning habitat to reach specific
spawning areas in Yampa Canyon. However, all adult-sized Colorado squawfish
may not spawn annually, and a lack of long-distance migratory behavior has
been associated with less than annual spawning and sexual immaturity (Tyus
1990; Wick et al. 1983).
Radiotelemetry studies in the Green River basin suggest that spawning is
concentrated in two major sites: (1) the lower 32 km (20 miles) of Yampa
River canyon; and (2) Gray Canyon of the Green River (Tyus 1985; Tyus and
McAda 1984; Tyus 1990; Wick et al. 1985) (see Figure 2). Spawning also is
suspected in Labyrinth Canyon in the Green River about 50 km (31.25 miles)
upstream of the Colorado River confluence (Tyus et al. 1987). This is
supported by the capture of many young larval fish (protolarvae) immediately
downstream of this reach (Valdez 1990). Radiotelemetry, collections of ripe
fish, and recaptures have confirmed long-distance migration to these locales.
These migrations average about 90 miles, and include both upstream and
downstream movements-(Tyus -1990; Wick et al. 1983). A total of 153 Colorado
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