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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was inadequate to provide a context for recovery goal development for either of
these species.

Downlisting and delisting goals are proposed within each criterion for each
species. Generally, for a species to qualify for downlisting to threatened, a
minimum number of populations are determined as necessary; all of these
populations must meet the distribution, recruitment and size structure goals for five
years; and a subset of these populations must meet an abundance goal. For
delisting, an additional population may be required to meet an abundance goal in
addition to maintaining the down listing requirements and/or all of the populations
designated as necessary must meet the goals set for abundance, recruitment and
size structure for a period of time under the trend criterion. This time period
approximates the species' generation time, which is estimated from age of sexual
maturity and mortality rate. For Colorado pikeminnow and humpback chub, other
differences in downlisting and delisting goals include increases in recruitment level
and frequency or the percentage of one of the size categories in the size structure
of the population.

Recovery goals for Colorado pikeminnow include populations in the Green,
Colorado, and San Juan river basins, though only two of these populations are
required to meet the goals listed for their respective criteria. Distribution
requirements are specified for the Green and Colorado River populations to
include the Yampa, Little Snake, White, Price, Duchesne, Gunnison, and Dolores
rivers (i.e. population segments in tributaries). Separate abundance requirements
for adult fish are specified for the three populations. Separate recruitment rates
and length frequency distributions are specified for the Green, Yampa and White
River population segments within the Green River population; and for the Colorado
and San Juan Rivers. These recruitment rates and length frequency distribution
requirements are based on 5-year rolling averages of annual estimates.
Frequencies of a specified threshold recruitment rate for downlisting or delisting
are based on annual estimates. An abundance trend requirement is specified for
the population segments in the Green, Yampa, White, Colorado, and San Juan
rivers. Differences between downlisting and delisting requirements among these
criteria include a 12-year abundance trend period for delisting, and frequencies of
occurrence for annual recruitment rates ~1 0% in 2 of the 5 years for downlisting.
and 4 of 12 years ~15% for delisting. The percentage range for the smallest size
category for the Colorado River population and the largest size category for the
Green River population segment must increase from 1-10% for downlisting to 5-
15% for delisting.

Recovery goals for humpback chub include five populations or population
complexes required for recovery, including the Black Rocks-Westwater Canyon
complex, the Little Colorado River-Grand Canyon complex, the Yampa-Whirlpool-
Split Mountain complex, Cataract Canyon, and Desolation-Gray Canyons. Two of
these five populations must meet an abundance requirement for downlisting and
three populations must meet this requirement for delisting. All five populations

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