9523

• UCREFRP Catalog Number: 9523
• Author: Birchel, G. J. and K. Christopherson.
• Title: Survival, Growth and Recruitment of larval and Juvenile Razorback Suckers ‎(Xyrauchen texanus)‎ Introduced into Floodplain Depressions of the Green River, Utah.
• USFW Year: 2004.
• USFW - Doc Type: Vernal.
• Copyright Material: NO

EXECUTIVE SUMMARY
Floodplains are presumed to be important rearing habitat for the endangered
razorback sucker (Xyrauchen texanus). To help recover this endemic Colorado River
Basin species, the Upper Colorado River Endangered Fish Recovery Program
implemented a floodplain acquisition and enhancement program. Levee removal was
initiated in 1996 as one component of this floodplain restoration program. The goal of
~ the Levee Removal Study was to evaluate the system responses to levee removal and
make specific recommendations concerning the value of floodplain/river reconnecting
for endangered species (specifically razorback sucker) recovery. Razorback suckers
were not collected in floodplains during the Levee Removal Study, which may be
attributed to the low razorback sucker population in the river. Therefore, data specific
to razorback sucker use of the floodplain was not available. This was not a stocking
evaluation, rather the stocked fish were used as a tool to learn how razorback sucker
may use the floodplains. Age-1 and larval razorback sucker were stocked into
depression floodplain wetland habitats along the Middle Green River in northeastern
Utah. Age-1 razorback suckers were stocked during the spring of 1999 and 2000 into
. three floodplain depressions. At the time of stocking each floodplain site contained
numerous nonnative fish including: black bullhead (Ictalurus melas), fathead minnow
(Pimephales promelas), green sunfish (Lepomis cyanel/us) and carp (Cyprinus carpio).
The, goal of this study was to evaluate if floodplain depressions containing nonnative
fishes can still provide effective rearing habitat for naturally produced (wild) razorback
sucker. Specific objectives intended to address questions remaining from the Levee
Removal study include:
A) Determine larval razorback sucker survival rates in nonnative fish
dominated environments.
B) Determine growth rates of larval and juvenile razorback sucker in
nonnative dominated environments.
C) Determine if razorback sucker leave floodplain depressions and recruit to
the river.
D) Assuming C is true, determine how long fish use floodplain depressions
before leaving and what factors trigger movement from floodplain
~ wetlands for the river.
Survival of larval razorback sucker stocked into the floodplains was not detected
by sampling. The exact cause of larval razorback sucker mortality in the sites is
unknown, however, some possibilities include; predation, insufficient stocking densities,
poor water quality and failure of stocked larval fish to use available food resources.
Survival of age-1 razorback sucker stocked in 1999 was estimated for each
study site after the first growing season (fall 1999) and after one year (spring 2000).
Estimated survival for fall 1999 ranged from 37% to 57% During spring 2000,
overwinter survival was estimated at 56% to 73%. Razorback sucker summer survival
was significantly reduced in 2000 because of below average spring flows and drought
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