9378

• UCREFRP Catalog Number: 9378
• Author: Nesler, T. P.
• Title: Recovery of the Colorado River Endangered Fishes
• USFW Year: 2000.
• USFW - Doc Type: Biological recovery goals and criteria for Colorado pikeminnow, Humpback chub, Razorback sucker & Bonytail.
• Copyright Material: NO

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Executive Summary

Quantified recovery goals for the four federally-listed Colorado River fish
species- Colorado pikeminnow, humpback chub, razorback sucker, and bony tail,
are recognized as vital benchmarks to guide progress and define endpoints within
the recovery program. Recovery criteria are identified using population
parameters that can be determined or estimated annually from field data using
consistent methodology. The premise of this approach is that the fish data
available from standardized monitoring and population estimation sampling is
sufficient to develop measurable goals for down listing and delisting. The focus of
recovery goal development is the inclusion of populations of the listed fishes and
their habitat where a potential for persistence appears feasible based on existing
biological data.

The over-riding criterion defining recovery is that these populations are
maintained through recruitment of young fish generated from natural reproduction
in the wild. Other biological criteria used to define recovery include number of
populations, distribution, abundance, recruitment to the adult population, and
population structure. The goals for these criteria are intended to describe viable,
self-sustaining populations with successful reproduction, survival and growth. The
goals for number of populations, distribution and abundance criteria meet minimum
genetic viability standards, promote genetic diversity and demographic stability,
and reduce impacts from potential catastrophic population reduction or loss.
Distribution, recruitment and population size structure (length frequency
distribution) criteria describe dynamic processes of annual reproduction, survival of
year classes, and dispersal of fish throughout their habitat. The abundance trend
criterion and the range and frequency attributes of the recruitment and population
size structure criteria describe stability yet recognize natural population level
dynamics and variability.

Population estimates and length frequency distributions were developed for
all riverine populations of the endangered fish species from 1991-1997, if data
were available, for the purpose of determining current status and trends in these
populations and examining variability in population parameters over time. This
data was compared to results of other studies when possible, and used to examine.
recovery goals in context with estimates derived from empirical data or models.

Only biological recovery goals are presented. If the populations of listed
fish species are documented to be meeting these criteria for delisting, then it is
reasonable to assume that the necessary habitats and ecological requirements are
in place to maintain these populations. As a result of the 8-12 year abundance
trend delisting requirement that portrays population stability over a generation time,
it is also reasonable to assume that the five listing factors addressing threats are
being adequately mitigated in the current environment. The recovery goals not
presented are the institutional mechanisms whereby the above environment is

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