WSP12629 ‎(2)‎

• File Number: 8240.200.10.H
• Description: Upper Colorado River Endangered Fish Program
• Basin: Colorado Mainstem
• Date: 10/15/2001
• Author: Thomas P. Nesler CDOW
• Title: Stocking Plan for Endangered Colorado River Fish Species in Colorado
• Water Supply Pro - Doc Type: Publication

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populations except for the population of large, senile adults inhabiting Lake Mohave. If the
dramatic disappearance of bonytail were the result of hybridization catalyzed by habitat
modification, there has been no evidence of such a significant event in the genetic material of the
remaining Gila populations sampled for such via mOlpho-meristic, allozyme, and DNA techniques
(Dowling and DeMarais 1993, McElroy and Douglas 1995). This hybridization event would
have, in effect, subsumed the bonytail population genome into the genetic material of the other
Gila species virtually without a trace. This is difficult to accept, and makes the supposition that
hybridization between stocked bonytail and humpback chub or roundtail chub to the detriment of
the latter two species also less credible.

In light of the above information, the risk of extinction and permanent loss of wild bonytail
populations is considered to outweigh the risk of potential hybridization from reintroduction
stocking. The Recovery Program has approved stocking of bonytail independent of any
hybridization studies and stocking has occurred in two river reaches in Utah, and in the two target
reaches in Colorado.

Stocking Plan - Colorado pikeminnow (Table 1)

Colorado pikeminnow are designated as the third priority species in this plan. This ranking
results from the relative abundance of Colorado pikeminnow populations in the Yampa, White,
and Colorado rivers compared to razorback sucker and bonytail. A primary objective of stocking
Colorado pikeminnow in Colorado is to restore extirpated and marginal adult populations in river
reaches upstream of instream barriers. Through stocking we will strive to establish adult
populations that will spawn in available canyon habitat and increase larval production and
recruitment in the Colorado River and Gunnison River populations in the short term, while other
recovery actions target improvement of survival and recruitment of this species to preclude the
need for augmentation in the long term. Since the construction and operation of the Redlands fish
passage structure, which has resulted in the passage of early-adult stage Colorado pikeminnow into
the Gunnison River, and purposeful translocation of adult Colorado pikeminnow from below the
barrier to the river above, mixing of the genetic material between the populations occurring in the
two rivers is being accomplished, and is acceptable. Results from Anderson (1999) have
demonstrated that some spawning and production of drifting Colorado pikeminnow larvae
occurred in the Gunnison River above the Redlands diversion dam in 1994-1996. Planning for
the acquisition of the necessary fish and development of an acceptable mating strategy to
incorporate existing genetic material from Gunnison River Colorado pikeminnow into the
production of progeny needed for stocking should be initiated as soon as possible by the
Propagation Coordinator for the Recovery Program. This may be accomplished with the capture
of a single, ripe adult Colorado pikeminnow (male or female) annually from the Gunnison River
and use of this individual's gametes in a paired mating in the Colorado River spawning strategy.

Currently, the propagation strategy for Colorado pikeminnow is to conduct streamside
spawning of captured, wild, ripe adult fish from the Grand Valley reach of the Colorado River.
Mated pairs will be created with the fish available from each year's capture efforts. All adults

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