9442

• UCREFRP Catalog Number: 9442
• Author: Muth, R. T. and T. E. Czapla.
• Title: Workshop Summary
• USFW Year: 2002.
• USFW - Doc Type: Designing Methods to Evaluate Stocked Fish in the Upper Colorado River, Green River, and San Juan River Subbasins.
• Copyright Material: NO

Whether suitable mainstemand/or floodplain habitat for razorback sucker reproduction
and rearing be available if appropriate flows are delivered to the three reaches identified
in the Colorado and Gunnison rivers for reintroduction.
The type of gear and sampling strategies that would yield the mo~t effective means of
monitoring and detennining population densities for adult razorback sucker.
Whether the survival rate for razorback sucker stocked at <200 mm is representative of
their low survival in the wild.

4.2 Status of Wild Razorback Sucker in the Green River Basin, Utah and Colorado,
Determined from Basinwide Monitoring and Other Sampling Programs (Bestgen et
al. 2002)

Designed to measure response to management actions (e.g., nonnative fish removal). A small
wild fish population exists. Adults were found in middle and lower Green, plus Yampa rivers,
but mostly in middle Green (Escalante spawning bar area). Basin-wide sampling insufficient for
abundance estimate. Existing data were used to estimate population trend, which was declining.
Modde estimated 500 adults in 1992. Current wild population is consistent with expected
mortality rates (<100 wild adults). Survival rates had not changed, but aging population appears
to be dying off with no recruitment. Good numbers in 1998-99. Light trapping found some
larvae; but they were not abundant. Downward trend was evident. Some stocked fish (~50)
captured.

Recommendations
Fish do tend to disperse downstream, therefore, stocking sites should be planned
accordingly.
Continue light trapping for larvae. Most wild fish will be gone soon, so most larvae
captured from here on should come from stocked fish.
Need to look for evidence ofrecruitment. Recruitment estimates could be confounded by
unmarked stocked fish that escape from wetlands.

4.3 Stocking and Monitoring Hatchery-reared Bony tail in the Colorado and Green
Rivers, 1996-2001 (Badame and Hudson 2002)

Purpose and objectives were to 1) reintroduce bony tail into the Colorado and Green rivers, 2)
detennine the appropriate number and size of bony tail to stock to maximize survival, 3)
detennine dispersal and potential habitat overlap with other Gila spp., and 4) detennine if flow
training results enhance survivorship.

Hatchery production used the broodstock from Dexter National Fish Hatchery to produce fry that
were raised at Wahweap State Fish Hatchery. Ten rearing ponds were used. h1 the first summer
of growth, bony tail reached approximately 120 mm TL. During 1996-] 998, all fish were PIT
tagged; 1999-2000 all fish were coded wire tagged. In the Colorado River, fish were stocked at
Dewey Bridge (RM 96); in the Green River, fish were stocked at Green River, UT (RM 120).
Numbers stocked are shown in Tables 4 and 5. Recapture effort is shown in Tables 6 and 7.

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