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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using these parameters/criteria are indicative of viable, self-sustaining populations
with successful reproduction, survival and growth. The abundance criteria are
intended to surpass minimum standards for genetic viability. Genetic diversity and
demographic stability are promoted through the distribution criterion, which
requires populations of the listed fish species to be comprised of multiple existing
or new population segments. The population abundance criteria are set above a
minimum threshold to minimize inbreeding and contribute toward maintaining
existing genetic diversity. Recruitment and length frequency distribution criteria
are a measure of the dynamic processes of differential annual reproduction and
survival of year classes. Recruitment into population segments indicate the
movement or dispersal of these year classes throughout their habitat. The
abundance trend criterion and the range and frequency attributes of the
recruitment and length frequency criteria are important for defining stability while
recognizing natural population level dynamics and variability, and for identifying
negative trends or conditions for these populations. The use of rolling averages for
defining recruitment rate and size category ranges is intended to dampen annual
variation in estimation of the criterion due to natural or sampling factors, and are
based on empirical data from these same populations demonstrating a persistence
and stability over time. Rolling averages are estimated using a proscribed number
of sequential annual estimates, and use all estimates within the available time
period up to the most recent annual estimate (e. g. 1991-1993, 1992-1994, 1993-
1995, etc.). The use of frequencies of a threshold recruitment rate in conjunction
with the range of stability is intended to maintain the occurrence of recruitment
rates in the higher end of the range of stability. Peaks in recruitment rates are
necessary periodically to offset naturally occurring periods of low recruitment, and
boost adult population numbers when environmental conditions are favorable for
survival through the late-juvenile life stage. This recruitment pattern is considered
an adaptive strategy for a long-lived species in a variable environment with
uncertain and varying reproductive success.

Distribution of multiple populations and population segments over a wide
geographic area provide demographic stability and security from the potential risk
of a catastrophic event significantly impacting the species or anyone population by
providing redundancy. Maintaining connectivity between these population
segments and populations is considered important to allow gene flow between.
adjacent populations or permit recolonization. Maintaining connectivity between
populations via passage structures or translocation of wild fish around instream
barriers is desirable if these barriers cannot be removed. Restoration stocking to
accelerate recolonization of vacant habitat is also desirable. In contrast, if
augmentation stocking is required to maintain population abundance, this condition
is considered a failure to meet a self-sustaining status.

The data available through the Recovery Program centralized database
maintained by U.S. Fish and Wildlife Service in Grand Junction have been
analyzed for the four endangered fish species. This database is a cumulative
collection of all endangered fish data derived from Recovery Program projects

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