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

numbers needed over the next five years were estimated according to biologically-based
population objectives, and thereby permit the estimation of propagation facilities required to
meet these stocking objectives. The plan will present required objectives, justification and
risk assessment for each species' proposed stocking scenario.

Stocking Objectives and Relation to Recovery Objectives

1) To restore populations of razorback sucker, bonytail, and Colorado pikeminnow to
unoccupied river reaches within Colorado,
2) To augment very small populations of razorback sucker and Colorado pikeminnow in
occupied river reaches in Colorado,
3) To establish populations of these three fish species comprised of at least three age
groups at a desired population abundance level (fish/mile).

Recovery of these fish species is described as a number of self-sustaining populations within
species' recovery plans. Specific quantification of recovery criteria for downlisting and
delisting each species remains an incomplete task. The Recovery Program's Genetics
Management Plan (Wydoski 1995) and Interim Management Objectives (Lentsch et al. 1998)
provide preliminary direction for species and reach priorities and abundance targets for each
population. This plan further specifies target objectives for distribution, abundance, and
composition of stocked populations of three of the four federally-listed Colorado River fiSh
species for river reaches within Colorado. With achievement of the three objectives above,
the fundamental building block for naturally-functioning and self-sustaining populations will
have been established. This will contribute to recovery via expanded distribution and greater
abundance of these species in presently unoccupied or isolated habitats and further reduction
of extinction probability. Presence of these stocked populations will contribute to recovery
by making it possible to identify limiting factors pertaining to spawning, reproduction,
sUlVival, and recruitment that cannot be assessed under the present circumstances of low to
non-existent population numbers. Attempted spawning and the production of viable eggs and
larvae by these stocked populations will constitute the frrst step in conversion to desired
natural function and self-sustaining status for these stocked populations.

For razorback sucker and bonytail, no other recovery action provides an effective and
timely means of restoring wild populations in those river reaches designated within the
Genetics Management Plan. Success in achieving these stocking objectives could result in
the establishment of 1-2 bonytail populations where there are presently none; and 1-3
razorback sucker populations in the Colorado River to complement the existing two in the
middle and lower reaches of the Green River. For Colorado pikeminnow, success would
result in an expanded Colorado River population with potentially new distinct spawning
aggregations in Debeque Canyon of the Colorado River; Dominguez Canyon in the Gunnison
River, and Dolores Canyon in the Dolores River. Constnlction of fish passage stnlctures. on
the Colorado River to achieve connection and dispersal similar to that obselVed at Redlands
on the Gunnison River remains a critical component of recovery actions necessary to
complement restoration stocking.

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