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

probably in the late young-adult stage as evidenced by collection data
(Tyus et al. 1982), which show (UCRB 1984) the high concentration areas
for Juvenile Colorado squawfish are in the lower sections of the mainstem
Green River, but the only high concentration areas for adults in the
mainstem are in upper sections. Furthermore, Figure 5 demonstrates this
concept applied to the whole Green River Basin. Young Colorado squawfish
are relatively abundant and juveniles common in the mainstem Green
River, however, in the major tributaries (White and Yampa rivers 1981),
where adults predominate, juveniles and young are rare.
Habitat selection appears to be the driving force for migration.
Hence adults move up to 200 km to spawn in whitewater canyons. After
hatching, young larva can drift downstream and occupy warm shallow
habitats where rapid growth is possible. These movements also aid in
reducing intraspecific predation since the adults and young tend to
concentrate in different river sections.
• Reproduction
The spawning of P, Lucius occurs in the mid to late summer, under
-- a-decreasing.flow regime, making it unusual among most stream fishes
which spawn in the spring and early summer with rising water levels.
As with other potamodromous riverine species, timing of reproduction
becomes very important; and studies of spawning P. Lucius (Archer et
al. 1984) indicate the~fi_sh is apparently able to time its spawning to
coincide with the descending limb of the hydrograph, a time when
downstream transport of young would distribute them into the shallow