7834

• UCREFRP Catalog Number: 7834
• Author: Burdick, B. D. a. R. B. B.
• Title: Experimental Stocking Of Adult Razorback Sucker In The Upper Colorado And Gunnison Rivers.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

stocking.survival. Stock equal or near equal numbers of fish from
each family lot to minimize the potential loss of genetic diversity.
Document fish condition prior to release. Body condition at the time
of stocking should be compared with fish that may be later recaptured.
Five-thousand razorback sucker between 150-400 mm were stocked in Lake
Mohave and researchers are presently compiling catch data to evaluate
the relation between survival and size at release. Results of this
study may provide insight into the optimum size to stock. However,
sizes that promote optimum survival in lower basin reservoirs may not
be appropriate to enhance post-stocking survival for razorback sucker
released in upper basin riverine reaches.
3. Time of Year to Stock. Stock captive-reared razorback sucker in the
spring prior to runoff, if the target fish have attained adequate
size. If adequate numbers of captive-reared fish are available from
each family lot, stock both in the fall and spring of each year to
determine the best time of year to stock. After two years of data
collection in the San Juan River, the preliminary recommendation is
that stocking in the spring is best because it allows adequate dime
for fish to adapt to their new riverine habitat before winter.
However, if the fish have not attained the target size for stocking
prior to spring runoff, spring stocking may have to postponed and fish
stocked the following fall.
4. Available Food Resources. Collect food availability and density data
(zooplankton densities) from potential reintroduction sites prior to
stocking to determine if the habitat selected has suitable food
resources for released fish. Equally important as the temporal and
spatial selection of sites to stock captive-reared razorback sucker is
the consideration of available food resources at the time of release.
Timing the release of hatchery-produced fish in backwater river
habitats to coincide with optimum densities of food resources, i.e.,
large zooplankton blooms, may increase initial post-stocking survival.
Domestically-produced and reared, sub-adult razorback sucker will be
released in backwaters in the lower Green River to address if survival
of these fish is related to the timing of zooplankton densities.
These studies will be conducted by the Biological Research Division of
the USGS in 1998.
5. Conditioning/Acclimation. Determine if post-stocking survival might
be enhanced if captive-reared fish are physically conditioned to flow
prior to stocking. Determine if post-stocking behavioral stress can
be reduced and survival increased if fish are allowed to slowly
acclimate in a backwater before migrating to other riverine habitats.
6. Stock Large Numbers of Various Sizes of PIT-tagged Razorback Sucker.
Utilize other methods beside telemetry to assess stocking survival and
residence. Each stocked fish should be marked with a unique,
identification code or number. Intensive monitoring should follow to
determine post-stocking survival. Stocking large numbers of fish is
required to insure that adequate numbers of fish can be recaptured to
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