9489

• UCREFRP Catalog Number: 9489
• Author: Mueller, G.
• Title: The Role of Stocking in the Reestablishment and Augmentation of Native Fish in the Lower Colorado river Mainstream ‎(1998-2002)‎.
• USFW Year: 1998-2
• USFW - Doc Type: 03-288,
• Copyright Material: NO

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habitat puts the species at a much higher predation risk.
Through a process of trial and error during the past two decades, managers are now stocking large natives to
increase their survival. Small native fish simply have not survived. While this improves short-term stocking
survival, it ignores or at least delays dealing with the predation issue. Current stocking programs have
reestablished or augmented relatively small populations of bonytail, razorback, and tlannelmouth suckers
between Davis and Parker Dams. All three species are better offthan they were a decade ago in this section of
the river. Unfortunately, bonytail and razorback sucker will only maintain a presence in the Colorado River
main stem through continued stocking and it remains to be seen if management agencies will make that long-
term commitment.
While the gains for the bonytail and razorback sucker have been difficult, the successful reintroduction of
tlannelmouth sucker highlights the ecological changes that have taken place and suggests this, and possibly
other channel oriented species (i.e., Gila robusta) could be established. In contrast, there is no evidence to
suggest we can expect similar recruitment or expansions for bonytail and razorback sucker. Their dependence
on slack water habitat leaves their young vulnerable to overwhelming predation.
Recovery in the main stem will only be accomplished with a dramatic decrease and possibly a total removal
of nonnative species. After ten years and over $6 million in expenditures to remove nonnative fish it appears
this philosophy is neither technically nor politically viable. In the meantime, stocking is the only alternative
available to insure these species don't disappear. The only viable option appears the creation and maintenance
of small, isolated refuge communities where these species have shown they can produce young.

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