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

D-RAFT
Loss of fish habitat and habitat fragmentation due to stream blockage could
pose a threat to the recovery effort and has been implicated in the systematic
loss of the fish. Sheldon (1988,) found that alterations of river drainages by
fragmentation leads~to a reduction of species diversity and pecies
extinction. In the upper Colorado River, blockage of the Gunnison and upper
mainstream by diversion dams have no doubt restricted access of-the fish to
presumed habitats (Valdez et al. 1982). Construction of Flaming Gorge Dam
buried inundated spawning habitats and blocked upstream passage. Construction
of Taylor Draw -Dam on the White River has blocked the movement of upstream,
return migrants (Martinez 1986a) and resulted in a loss of about 80 km
(50 miles) of adult habitat from which mature fish contributed to the spawning
aggregations in both Gray and Yampa canyons (Tyus et al-. 1981). Fragmentation
of the rivers in the Lower Basin undoubtedly restricted movement over much of
the historic range of the Colorado squawfish.
In September 1962, the area of the Green River now impounded by Flaming. Gorge
Dam was treated with rotenone in order to establish more favorable conditions
for game fish species. This poisoning effectively eliminated Colorado
squawfish in the reservoir basin, and an accident occurred in which a small
proportion of the toxic substance apparently travelled downstream past a
detoxification station to the vicinity of Dinosaur National Monument. Banks
(1964) noted a significant reduction in the number of species captured at four
stations within the Monument shortly after the accidedtal treatment. The
greatest reduction appeared to occur at the Gates of Lodore in the northern,
and most upstream, portion of the Monument, while the least impact was noted
at a downstream site. However, Binns et al. (1963) concluded that little
long-term impact to the fish species composition had resulted from the
treatment.
Colorado squawfish have disappeared from areas upstream of reservoirs (e.g.,
Salt River above Roosevelt Lake, Arizona; Green River-above Fontenelle and
Flaming Gorge dams, Wyoming; San Juan River above Navajo Reservoir, New
Mexico) and in reaches that appear little changed from predevelopment
conditions. Reasons for these disappearances or declines are not fully
understood, but probably involve subtle changes in habitat, competition and
predation from introduced species, blockage of spawning migrations, lack of
suitable spawning habitat, post-dam eradication programs, and/or loss of adult
fish from angling. In summary, the absolute cause for the decline of Colorado
squawfish is~not fully understood but is probably re]ated to a combination of
factors, including direct loss of habitat, changes in flow and temperature,
blockage of migration routes, and interactions with introduced fish species.
Sensitive Areas and Priority Recovery Areas
Sensitive Areas
The Biological Subcommittee of the Upper Colorado River Coordinating Committee
developed criteria and prepared a list of sensitive areas depicting the
location of important spawning, nursery, juvenile, and adult habitats, both
past and present, in the Upper Basin (U.S. Fish and Wildlife Service 1987)
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