2525

• UCREFRP Catalog Number: 2525
• Author: U.S. Fish and Wildlife Service.
• Title: 25th Annual Recovery Program Researchers' Meeting.
• USFW Year: 2004.
• USFW - Doc Type: Moab, Utah.
• Copyright Material: NO

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fish's environment. Chronological information from otoliths coupled with analysis of
otolith chemical makeup enables identification of chemically distinct environments
occupied over the lifetime of a fish. Spatial distributions of selenium concentrations and
naturally-occurring stable isotope signatures of carbon, nitrogen, hydrogen, and strontium
within the Colorado River and adjacent floodplain ponds, tributaries, and irrigation
ditches indicate that these elements have good potential to serve as natural markers of
non-native fish origins and movements.
Predator Removal and Control in the Colorado River Mainstem: What have we
learned?
Mueller, Gordon
USGS, Denver, CO
Predator removal programs have gained popularity, especially in the Colorado River
Basin. Non-native fish control features have benefited the recovery of several native
salmon and spring fish; however, these successes have been limited to headwater streams
and small, isolated ponds or springs. Never-the-less, these same approaches are being
applied to mainstem species on the belief that removing non-native predators will benefit
natives. Unfortunately, after 10 years, the expenditure of >$4 million (USA) and the
removal of >1.5 million fish, we have yet to see any positive response from native
communities. This failure is primarily due to the severity of the problem coupled with
institutional issues and constraints. Predation is actually getting worst in some areas.
This leads to the obvious question; is predator removal or control in the mainstem
feasible? If not, recovery for some species may not be practical in the conventional
sense. This review examines what's been attempted, what has worked, and what has not
in the Colorado River mainstem and provides recommendations.
Suppression of populations and reproduction in a nonnative fish: sensitivity of
various life history stages of red shiners to environmental manipulation.
Hilwig, Kara D., Graduate Student, and Dr. W. Linn Montgomery
Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ
Nonnative fishes may contribute to declines of native fishes in the southwest United
States and elsewhere. Strategies to recover native species often include removal of
nonnative species, but complete removal is unrealistic, especially where nonnatives have
established reproducing populations. An alternative approach would expose both types
of species to conditions that selectively suppress survival or reproductive success of
nonnative species. We seek environmentally realistic (e.g., non-extreme) conditions that
suppress survival o f e arly t ife h istory s tages (eggs, l arvae) o f red shiners (Cyprinidae:
Cyprinella lutrensis). We assess survival of eggs and larvae subjected to physicochemical
variables (temperature and salinity) in laboratory tests. Data indicate red shiner eggs and
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