9713

• UCREFRP Catalog Number: 9713
• Author: VanHaverbeke, D.R.
• Title: Stock assessment and fisheries monitoring activities in the Little Colorado River within Grand Canyon during 2004.
• USFW Year: 2005.
• USFW - Doc Type: U.S. Fish and Wildlife Service
• Copyright Material: NO

INTRODUCTION

With the passage of the Grand Canyon Protection Act in 1992, the Glen
Canyon Dam Adaptive Management Program was initiated. The center of the
program is the Adaptive Management Work Group (AMWG). The AMWG has
the responsibility of defining management objectives associated with the ,
resources downstream of Glen Canyon Dam, and making recommendations for
the development of a long-term monitoring program to assess those resources.
The Grand Canyon Monitoringand Research Center (GCMRC) is responsible for
implementing the long~term monitoring program and assuring that it is fulfilling
the needs of the AMWG. The humpback chub (Gila cypha; HBC) is particularly
important due to its status as a federally listed endangered species (U.S. Office
of the Federal Register 32:48 [1967]:4001).

A tremendous amount of research has been conducted to gain a better
understanding of HBC in Grand Canyon over the last 20 years. Some of this
work has reported on population status (Kaeding and Zimmerman 1983, Valdez
and Ryel1995, Douglas and Marsh 1996), while other studies have focused on
natural history and ecology (e.g., Robinson et al. 1998, Gorman and Stone 1999,
Clarkson and Childs 2000). Because the AMWG has a need to effectively
assess the impacts of the operation of Glen Canyon Dam on HBC and to
evaluate whether fish management objectives in Grand Canyon are being met,
GCMRC initiated a program in 2000 that focused on stock assessment and long-
term monitoring of Grand Canyon fishes.

GCMRC's long-term monitoring strategy for the Little Colorado River (LCR)
HBC population is essentially a four pronged approach:

1. Annual spring and fall HBC abundance assessments in the lower 13.6 km
of the LCR.

2. Annual spring HBC relative abundance assessment in the lower 1200 m of
the LCR.

3. Annual spring/summer HBC relative abundance assessment in the LCR
Inflow (mainstem Colorado River mile 57 to 65.4).

4. Annual assessment of the overall LCR HBC population abundance and
recruitment utilizing the age structured mark-recapture model (ASMR)
developed by GCMRC (Coggins et aI., In prep.).

This strategy provides a comprehensive view of the dynamics of the LCR HBC
population whereby each of these programs is designed to complement each
other.

In order to address item 1 above, in October and November 2000 the USFWS
undertook an effort to estimate the fall abundance of HBC in the LCR (Coggins
and Van Haverbeke 2001). Briefly, the strategy was to obtain a closed
population estimate of HBC in the LCR via a two pass mark-recapture effort.

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