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

Mortality was not immediate but delayed following release for razorback
sucker stocked both in the Upper Colorado and Gunnison rivers. The low number
of radio contacts in 1995 suggests either radiotag failure or missing fish had
moved outside the tracking search routes. Three habitat types used most
frequently were main channel (47X), backwaters (23X), and eddy/pools (16X). Six
control fish held for observation in ponds at Horsethief State Wildlife area all
retained their radiotags. Four of these six control fish were later stocked in
the Gunnison River; two of the control fish in the ponds died four months
following handling and radiotag implantation which was attributed to a bacterial
infection not associated to the surgical incision.
Stocking different sizes of razorback sucker and determining the optimum
size to release should enhance post-stocking survival. Post-stocking survival
might be enhanced if captive-reared fish are physically conditioned to flow prior
to release. Conditioning captive-reared fish prior to stocking may
physiologically and behaviorally prepare them to adapt faster and survive in
riverine environments.
Recommendations include, 1) stocking fish as far upstream as possible due
to the predominantly downstream dispersal of fish immediately following release.
In the Gunnison River, fish should be stocked immediately downstream of Hartland
Diversion Dam; the most feasible stocking location being Confluence Park boat
launch. In the Upper Colorado River, fish could be stocked at Rifle (RM 240.7);
2) determining the optimum size of razorback sucker to stock to increase post-
stocking survival by evaluating the survival and performance of different sizes
of hatchery- and pond-reared razorback sucker to be stocked over the next 4 years
in the Gunnison River; 3) stocking captive-reared razorback sucker in the spring,
if the target fish have attained adequate size; 4) collecting 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; 5) determining if post-stocking survival might be
enhanced if captive-reared fish are physically conditioned to flow prior- to
stocking; 6) determining 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 habitat; 7) stocking large numbers of various-sized
razorback suckers, each marked with a unique, identification code or number,
followed by intensive monitoring; and 8) recapturing stocked fish at 4 to 6-week
intervals to assess body condition and health, growth, and assessing if any
complications related to handling and tagging procedures occurred. Planned in
situ river acclimation and conditioning studies with captive-reared, sub-adult
razorback sucker might also prepare released fish to adapt better physiologically
and behaviorally and provide insight into increasing post-stocking survival.
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