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

Provide Recommendations for the Number and Size
for Stocking Razorback Sucker (Objective No. 6)
Because only sub-adult and adult fish were stocked in this study, it was
impossible to determine if smaller sizes of razorback sucker would have had
better post-stocking survival. An experimental field study to be conducted
between 1996 and 2000 will evaluate the relation between survival of stocked,
captive-reared razorback sucker and size at release into the river. Results of
this study are intended to provide additional data for the number and size of
razorback sucker to stock (see section on "FUTURE STOCKING").
CONCLUSIONS
The following were conclusions from the research of this study:
1. Stocked, radiotagged razorback sucker initially moved downstream.
Healthy fish appeared to move back upstream near their release sites.
Stress may have had a relationship on downstream range--highly
stressed fish may be more susceptible to downstream displacement.
2. Post-stocking survival was less than anticipated in both river
systems. Mortality was not immediate but delayed following release
for razorback sucker stocked both in the Upper Colorado and Gunnison
rivers. Most radiotagged razorback sucker died within 4 months
following stocking.
3. At the termination of the study, in the Upper Colorado River, 3 fish
were confirmed alive, 10 were missing, 2 were confirmed dead, and 5
were presumed dead. Confirmed mortality was 10%. Actual mortality
was likely as high as 85% if missing and presumed dead fish were
included.
4. For fish stocked in the Gunnison River during 1994 and 1995, 3 fish
were confirmed alive, 3 were missing, 2 were confirmed dead, and 17
were presumed dead. Confirmed mortality was 8%; actual mortality
might have been as high as 88% if missing and presumed dead fish were
included.
5. Although preferred habitats were not determined, most contacts were
with fish in the main channel.
FUTURE STOCKING
A razorback sucker stocking plan for the Upper Colorado and Gunnison rivers
for 1996 through 2000 that will supplement the earlier stocking plan (Burdick
1992) has been developed (Burdick et al. 1995) and accepted by the Recovery
Program. The later stocking plan outlines an expanded experimental field study
to determine survival and performance of stocked captive-reared razorback sucker.
The study will evaluate re-introduction stocking of razorback sucker as a
management strategy to develop self-sustaining populations in the Upper Colorado
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