WSP09678

• File Number: 8220.101.10
• Description: Colorado River-Water Projects-Glen Canyon Dam/Lake Powel-Glen Canyon Adaptive Management
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 5/22/2003
• Title: Status and Management Strategy for Humpback Chub in Grand Canyon
• Water Supply Pro - Doc Type: Report/Study

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Status and Management Strategy for
Humpback Chub in Grand Canyon

May 22, 2003

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Report of the Humpback Chub Ad Hoc Committee to the
Adaptive Management Work Group of the
Glen Canyon Dam Adaptive Management Program

1.0 INTRODUCTION

1.1 Background

In 2002 the Grand Canyon Monitoring and Research Center (GCMRC) reported a
continuing decline in the Grand Canyon population of humpback chub (Gila cypha)
(GCMRC 2003). Causes for the decline are unknown, but stock synthesis models
indicate lower recruitment for most of the previous 10 years.( /Jr,c"-,,Jr ,.,),

In response to concerns about the status of humpback chub on January 29, 2003,
the Glen Canyon Dam Adaptive Management Work Group (AMWG) created the
Humpback Chub Ad Hoc Committee and directed that the committee". .. will consider
actions to implement a comprehensive research and management program for the HBC
(humpback chub) ... (and make) a recommendation to the AMWG ...." The approved
motion further indicated that the Ad Hoc Committee would consist of individuals from
the AMWG, TWG (Technical Work Group), GCMRC, and science advisors. The Ad Hoc
was directed to develop recommendations and report to AMWG at a special session.
Meetings of the Ad Hoc Committee were held February 12, March 12, April I, 21, and
22, and May 6,19, and 20, 2003. Conference calls were held April 16 and 25, 2003.
Committee members are listed in Appendix A.

1,2 Charge to the Ad Hoc Committee

The Humpback Chub Ad Hoc Committee will consider actions to implement a
comprehensive research and management program for the humpback chub. They will
meet in preparation for making a recommendation to the AMWG.

2.0 STATUS OF HUMPBACK CHUB IN THE COLORADO RIVER BASIN

2,1 Status of Humpback Chnb Population Grand Canyon

An overview of the status and trend of the Grand Canyon population of humpback
chub was prepared by GCMRC for the AMWG on April 22, 2003 (see Appendix B).
That report stated that recent analyses of historical data on humpback chub in Grand
Canyon have caused considerable concern, because of uncertainties about the current size
of the population and the strong probability that the population has been declining
steadily for at least a decade. The most recent assessment indicates that the spawning

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