7282

• UCREFRP Catalog Number: 7282
• Author: U.S. Fish and Wildlife Service, R. I. P.
• Title: Final Recovery Implementation Program for Endangered Fish Species in the Upper Colorado River Basin.
• USFW Year: 1987.
• USFW - Doc Type: Denver, Colorado.
• Copyright Material: NO

b. The Service will (1) conduct studies to determine the desirability of
passing Colorado squawfish over the Taylor Draw Dam, and (2) prepare a
report on the biological merits of constructing a fish passage at
Redlands.
4.3 STOCKING OF RARE FISH SPECIES
Colorado squawfish and humpback chub are reproducing in the upper basin, but
their long-term reproductive success is unknown. The bonytail chub appears to
be in imminent danger of extinction since it has been found in insufficient
numbers to effectively support a viable population; only five individuals have
been captured in the upper basin in the past few years, all from the Colorado
and Green Rivers. Hybridization is suspected of being a problem among the
various species of chub. Recent data indicate that the razorback sucker is
very rare, and its population is limited to a small number of very old adult
fish; successful recruitment in the wild has never been documented.
Research with hatchery-reared fish may provide a method to effectively
increase rare fish populations to the level where deductions can be drawn
about their habitat needs and biological interactions and thus eventually
provide a mechanism to enhance their recovery. However, numerous factors that
affect the survival of any fish species, such as prey abundance, predation,
disease, habitat quality, or quantity, may also affect the survival of
introduced hatchery-reared fish. For example, 5 years of stocking the
razorback sucker in stretches of the lower basin has not resulted in any
significant documented poststocking survival, though 1986 field data indicate
an increase in return. In comparison, it has taken considerable genetic
coaxing through countless generations of more domesticated species like the
rainbow trout to produce fishes that are suitable for modified or new habitat
or to meet a variety of management needs, including survival in the wild, fast
growth, and even increased reproductivity.
The introduction of nonnative species has also led to the establishment of
viable populations that may prey upon or compete with the rare fish species
(see Section 4.4). Rare fishes of various ages/sizes should be stocked and
monitored to discern whether competition, predation, imprinting, homing,
survival, etc., are critical factors to the species' success. Grow-out ponds
may be an effective way of accomplishing several of these multifaceted goals.
All four species have been raised successfully in hatchery facilities in the
lower or upper basins and stocked in numerous areas in both basins. Stocking
success is low to unknown. There are presently hatchery and/or wild
populations of squawfish, humpback chub, razorback sucker, and bonytail chub
that can be used to rear sufficient numbers in hatcheries for research or
limited reintroduction. However, there is concern over genetic and disease
problems relating to these fish. The existing hatchery populations consist of
a few individuals that are relatively old and inbred. Efforts must be made to
improve and maintain genetically healthy and viable hatchery populations.
Asian tapeworms had occurred in these stocks and has also been found in the
upper basin populations of some of these fish.
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