8114

• UCREFRP Catalog Number: 8114
• Author: Nesler, T. P.
• Title: Five-year Stocking Plan for Endangered Colorado River Fish Species in Colorado.
• USFW Year: 1998.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

Introduction

The propagation and stocking of the Colorado River endangered fishes is recognized
as one of five primary approaches to attaining the recovery goals for the four listed species-
razorback sucker, Colorado pikeminnow (formerly squawfish), bonytail, and humpback chub.
The direction to perfonn tasks related to propagation, augmentation, and restoration stocking
are clearly identified in the Recovery Implementation Program report (U. S. Fish and Wildlife
Service 1987), the recovery action plan (U.S. Fish and Wildlife Service 1998), and the
annual propagation operation plan (Czapla 1997).

Three razorback sucker stocks, three Colorado pikeminnow stocks, five humpback
chub stocks, and one bonytail stock have been identified (Wydoski 1995). Populations of
these species in Colorado rivers that contribute to, or are included within the critical habitat
range of these presumptive stocks include razorback sucker and Colorado pikeminnow
populations in the Colorado River from Rifle downstream to the state line, and in the
Gunnison River from Delta downstream to its confluence as part of the Upper Colorado
River stocks, respectively for each species. Colorado pikeminnow populations in the Yampa
and White rivers contribute to the Yampa and Green River-Desolation/Gray Canyon stocks.
Presumptive stocks of humpback chub in Colorado include the populations in the Yampa
River and Colorado River at Black Rocks Canyon. Bonytail populations formerly occurred
in Colorado, based on captures and identifications of this species in the Yampa, Colorado,
and Dolores rivers in historic and anecdotal accounts (Tyus and Karp 1989, Kaeding et aI.
1986, Quartarone 1993), but are now extirpated. This species is now represented by only
one captive stock at Dexter National Fish hatchery in New Mexico. Relict wild stocks exist
in Lake Havasu and Lake Mohave in the Lower Colorado River Basin, but are comprised of
very old, senescent adults (USFWS 1990a).

This stocking plan provides the rationale for conducting restoration stocking of three
of the four endangered fish species in select rivers of western Colorado within the Upper
Colorado River Basin, and includes priorities among species and river reaches, genetics risk
assessment, and criteria for contribution to recovery success as well as expectations and
limitations.

Background

Within the Upper Basin, stocking plans have been created for only the razorback
sucker in the Colorado/Gunnison rivers in Colorado (Burdick et al. 1995) and in the middle
Green River in Utah (Wydoski 1996), and for the bonytail in the Green and Colorado rivers
in Utah (Lentsch et al. 1996). These plans were developed when the Recovery Program
designated razorback sucker and bonytail as priorities one and two, respectively, for
propagation and stocking due to their extremely precarious status in the wild. Within
Colorado in the Colorado and Gunnison rivers, numbers of wild razorback sucker were
insufficient for collection and use in a 5x5 breeding matrix to even attempt to develop
broodstock. Additionally, the highest number of razorback sucker remaining in Colorado,

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