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

A third approach for partial control involves restoring and managing
floodplain habitats to behave naturally. Habitats would be allowed to
flood and drain during spring flows, providing ephemeral floodplain
habitats. Nonnative fishes may use the habitats for the relatively
short period of time in which they are inundated, but they would not be
able to expand, as they do in permanent ponds and gravel pits. In some
instances (i.e., ponds filled by overbank flooding), fish that remain in
the habitats after the river subsides are stranded and their ultimate
fate is death unless the pond reconnects with the river before it dries
up. Some sites can contain water for several years while others dry up
through evaporation in the arid climate of the Upper Basin.

5. Manage nonnative fishes at locations, possibly throughout the Upper
Basin (via flow management, removal, etc.), where habitats are enhanced
or restored.

At specific locations, it may be possible to partially control some
species of nonnative fishes to some degree via mechanical removal
methods and/or chemical control methods such as spot-poisoning prior to
colonization by drifting razorback sucker larvae. Predators such as
northern pike, smallmouth bass, largemouth bass, and channel catfish may
be controlled through mechanical control methods. Partial control of
fish populations is a temporary measure because other undesirable (i.e.,
nonnative) fishes will fill the void (Wiley and Wydoski 1993). In
addition, fishes exhibit compensatory growth and fecundity associated
with growth that allows a high degree of resilency in reduced fish
populations.

There are several nonnative fishes that may be more vulnerable to high
spring flows than native fishes (Muth and Nesler 1993). Valdez (1990)
documented that red shiner populations were reduced after high
streamflows but exhibited resilency whereby the population structure was
similar to before the high flow events in several years. Furthermore,
some of nonnative fish species may be adversely affected by the
turbidity associated with high flows. Nonnative minnows that are both
predators and competitors with the endangered fishes include the
abundant red shiner and fathead minnow (Gutermuth et al. 1994; Haines
and Tyus 1990; Muth and Snyder 1995). While predation of razorback
sucker by the red shiner is limited to gape size (Crowl 1994), fathead
minnows prey upon catostomid larvae through group attack and then feed
on the pieces so that gape size is not as crit i ca 1 CDlJ1),SI.l,WQJ::1,99~J.

6. Use an experimental approach to enhance or restore floodplain habitats
by employing adaptive management.

Poor survival during the early life stages of the razorback sucker is
due in part to starvation since main channel habitats do not produce
sufficient zooplankton in the early spring when razorback suckers spawn.
Off-channel habitats in the Upper Basin have been shown to be extremely
productive for zooplankton (magnitudes higher than main channel or
backwater habitats). Therefore, enhancement or restoration of
floodplain habitats has been identified as an element in the Recovery

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