9660

• UCREFRP Catalog Number: 9660
• Author: U.S. Fish and Wildlife Service.
• Title: Colorado Squawfish Revised Recovery Plan - Draft.
• USFW Year: 1990.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

DRAFT
559. mm (22 in.) TL (n=120), but ripe females averaged 710 mm (28 in.) TL (n=7)
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
injection of 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 et al.
(1987) 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 et al. 1987; Wick et al. 1983). During the spawning
season, adult 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 et al. 1982a, 1982b). Homing behavior
and fidelity to spawning locations has .been indicated for Colorado squawfish
in the Green and Yampa rivers (Tyus 1985; Tyus et al. 1987; 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 and Karp (1989) report that migrating
Colorado squawfish pass through many miles of potential spawning habitat to
reach specific spawning areas in Yampa Canyon. However, not all- adult-sized
Colorado squawfish exhibit long-distance migratory behavior associated with
spawning, perhaps because they are immature (Tyus and McAda 1984; Wick et al.
1983), do not spawn every year (Wick et al. 1983), or spawn near the area in
which they reside.
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 et al. 1987;-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). Radiotelemetry,
collections of ripe fish, and recaptures-have confirmed long-distance
migration to these locales, sometimes 100 km (62.5 miles) or more, both
upstream and downstream (Tyus et al. 1987; Wick et al. 1983). A total of
112 adult squawfish were radiotracked by Service personnel from 1980-85
(Archer et al. 1985; Tyus et al. 1982b, 1987) and five were tracked by
National Park Service and Colorado Division of Wildlife workers in 1982 (Wick
et al. 1983). Collections made on the two known spawning grounds during
1981-85 produced 208 Colorado squawfish, of which 127 were ripe and 160 were
in breeding condition
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