9588

• UCREFRP Catalog Number: 9588
• Author: Bestgen, K. R. and e. al.
• Title: Population Status of Colorado Pikeminnow in the Green River Basin, Utah and Colorado.
• USFW Year: 2005.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

outcome of these environmental and biotic changes for the highly endemic fish fauna of
Colorado River Basin has been dramatic: two of the 35 native species in the basin are extinct, an
additional 18 are federally listed as threatened or endangered or are very rare, and most others are
listed by one or more basin states as declining (Stanford and Ward 1986; Carlson and Muth
1989; Bezzerides and Bestgen 2002; Mueller and Marsh 2002). Colorado pikeminnow is
federally listed as endangered under the Endangered Species Act of 1973, as amended (U. S. Fish
and Wildlife Service 1974).
Colorado pikeminnow, endangered bonytail Gila elegans, humpback chub Gila cypha,
and razorback sucker Xyrauchen texanus are the focus of the Recovery Implementation Program
(RIP) in the Upper Colorado River Basin (Wydoski and Hamill 1991). Recovery goals for
Colorado pikeminnow provide criteria that must be achieved before downlisting or delisting can
be considered (U.S. Fish and Wildlife Service 2002). The recovery criteria include demographic
attributes that describe the required number of sub-basin populations and individuals (adults and
juveniles) within each population, and recovery factor criteria that are directly linked to
management actions and tasks needed to minimize or remove threats.
Maintenance of a metapopulation is central to Colorado pikeminnow recovery, and
demographic criteria require "a genetically and demographically viable, self-sustaining
population in the Green River sub-basin; and self-sustaining populations that meet or exceed
estimated carrying capacity either in only the upper Colorado River sub-basin, or in both the
upper Colorado River sub-basin and San Juan River sub-basin". For consideration of
downlisting or delisting, specific demographic criteria for the Green River sub-basin portion of
the Colorado pikeminnow metapopulation require that, over the specified monitoring period, (1)
trends in abundance estimates for adults (Z 450-mm total length, TL) in both the middle and
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