9699

• UCREFRP Catalog Number: 9699
• Author: Brunson, R.E., and K.D. Christopherson.
• Title: Larval razorback sucker and bonytail survival and growth in the presence of nonnative fish in the Baeser floodplain wetland of the middle Green River.
• USFW Year: 2005.
• USFW - Doc Type: Utah Division of Wildlife Resources, Vernal, Utah.
• Copyright Material: NO

CONCLUSIONS
• Estimated larval razorback sucker survival in the experimental enclosures ranged
from 0 - 58% and growth rates averaged 0.6 mm/day in 2003 and 0.6 mm/day in
2004 in the presence of nonnative predators.
• Larval razorback sucker survival was detected 88 days following introduction at a
density as low as 4001arvae/acre.
• Bonytail larvae introduced sympatric with razorback sucker larvae at a density of
8,000 larvae/acre had an estimated survival of 16 - 17% in 2004 and a growth rate
of 0.6 mm/day in 2003 and 0.4 mm/day in 2004.
• Larval Bonytail survival was detected 106 days following introduction in 2003.
• Larval Bonytail survival was detected 66 days following introduction
sympatrically with razorback sucker larvae in 2004 at a density of 8,000
larvae/acre.
RECOMMENDATIONS
• Actions to identify monitor and manage variables and conditions necessary to
achieve entrainment of at least 4001arvae/acre should be implemented.
• Continue to manage floodplains based on the reset theory. Even with abundant
nonnative fish predators, these habitats are important to endangered fish and
should be used for recovery.
• During an average to high flow year, introduce larval razorback suckers into
floodplain sites that have reset to test this theory under more natural conditions.
This should include introducing larval razorback sucker at a density of at least
4001arvae/acre.
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