9522

• UCREFRP Catalog Number: 9522
• Author: U.S. Fish and Wildlife Service.
• Title: Life History of the Colorado Squawfish in the vicinity of Tusher Rapid.
• USFW Year: 1984.
• USFW - Doc Type: Vernal.
• Copyright Material: NO

especially in locations where the fish has been lost (Minckley, 1973)
have made cause-effect relationships difficult to prove. Recent research
in the Green River Basin (Figure .l) by the U.S. Fish and Wildlife Service
(Tyus and McAda 1984) resulted in the first location of the spawning
grounds of this species in 198], and identified migrations and movements
as important factors in the reproductive strategy of this species.
These findings have been substantiated by the work of Haynes et al.
(1984), Wick et al. (1983), Tyus (1985), and others.
Migration, Movement and Habitat Selection
The Colorado squawfish makes extensive use of migration in its life
strategy, and adults have been documented as homing to desirable spawning
sites (Tyus 1985). Figure 2 demonstrates the spectacular spawning
migrations to the Gray Canyon spawning site from 1981 to 1984. Migrations
of young are not so easily documented, but downstream transport of larva
have been noted by Haynes et al. (1984) and Tyus and McAda (1984). This
downstream transport is evidenced by peaks in abundance (Figure 3) of
young (Age 0) fish which occur downstream of the two confirmed spawning
sites in the Green River Basin (Figure 4). This enab]es the fish to
take advantage of river transport at the end of the flood period for the
dispersal of young from the upstream spawning grounds downstream to more
productive nursery habitat (Tyus and McAda 1984). Since this downstream
transport places young in lower river reaches, net long-term movement of
juveniles must occur to popu]ate adult areas upstream,