8287

• UCREFRP Catalog Number: 8287
• Author: Nelson, P., C. McAda and D. Wydoski.
• Title: The Potential for Nonnative Fishes to Occupy and/or Benefit from Enhanced or Restored Floodplain Habitat Adversely Impact the Razorback Sucker.
• USFW Year: 1995.
• USFW - Doc Type: \
• Copyright Material: NO

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INTRODUCTION

Many nonnative, warmwater fish species, that have become established in the
U~per Co 1 or~do ~iy_~x:__eClSi n, may occupy restored fl oodp 1 a in habitat. The
Recoveri Program endeavor-..at restoration of floodplain habitat is to provide
productive nursery areas for larval and juvenile razorback sucker. However,
there is a great potential for some lllillnatjv~ fi sli~s.-t6..fTourTsn in the
floodplain habitat and adversely impact larval and-juvenile razorback suckers
through Rr~gat ion and competition . Although razorback sucker still spawn and
produce larva~-fri the Green-River, poor survival during the early life stages
results in poor recruitment. Poor survival is attributed, in part, to
predation and competition from nonnative fishes and and possibly starvation
during the critical larval period. Present nursery areas consist of
backwaters along the main channels that are dominated by nonnative fish
species. Zooplankton production in the main channels is extremely low in the
upper basin and backwaters do not appear to produce sufficient numbers of
zooplankton that are needed for survival of the razorback sucker during their
critical larval period (Grabowski and Hiebert 1989; Mabey and Shiozawa 1993;
Papoulious and Minckley 1990). While the production of zooplankton is
excellent in off-channel flooded bottomland habitats, these habitats have been
disconnected from the main channels by levee construction. One current
Recovery Program thrust is to augment or reintroduce razorback suckers in
formerly occupied habitat of the Upper Colorado River Basin by reconnecting
floodplain with rivers. This would provide nursery habitat for rearing fish
until they reach a size when they are less vulnerable to predation and
competition. If this is achieved, razorback sucker may be able to survive the
recruitment bottleneck. Enhancing or restoring floodplain habitats, however,
will also be beneficial to nonnative, warmwater fishes that may adversely
affect razorback suckers through predation or competition.

The objectives of this issue paper were to:

1. Review available information on the composition of nonnative fish
species in selected reaches of the Upper Colorado River Basin.

2. Identify nonnative fish species that are likely to become established in
restored floodplain habitats and adversely affect larval and juvenile
razorback suckers.

3. Explore ways to prevent or reduce nonnative fishes in restored
floodplain habitats.

The geographic area considered in this issue paper include the mainstems of
the Green River (RM 0-345), Colorado River (RM 0-185), and Gunnison River (RM
0-75).

METHODS

Maps that documented the distribution and relative abundance of nonnative fish
species in the Upper Colorado River Basin in 1982 (Tyus et al. 1982) were
updated from information in various studies on the river reaches defined in
the geographic area considered in this issue paper. Native species and

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