9714

• UCREFRP Catalog Number: 9714
• Author: Ward, D., and W. Persons.
• Title: Little Colorado River fish monitoring 2004 annual report.
• USFW Year: 2005.
• USFW - Doc Type: Arizona Game and Fish Department.
• Copyright Material: NO

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sh Department (AGFD) began to monitor fish in the
Little Colorado River (LCR) asses the population trends and status of endangered humpback
chub (Gila cypha)(HBC) (R binso and Clarkson 1992). Annual standardized hoop net
sampling is conducted:6 30 0 ays to capture humpback chub during the spring spawning
period (Table 1). This program was discontinued in 2000 but then reinstated in 2002 at the
advice of the Grand Canyon Monitoring and Research Center Protocol Evaluation Panel (Anders
et al. 2001{ Catch-per-unit-effort (CPUE) indices derived from this monitoring program are
useful as independent validation for mark-recapture population models of humpback chub
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developed by Coggins and Walters (2001). With the exception ofthe period 2000-2001, the
lower 1200 meter sampling represents one of the most consistent, long-term sampling methods in
use for Grand Canyon fishes.

STUDY SITE

The study site is the lower LCR, 1200 m upstream from its confluence with the Colorado
River. The LCR in the study area iSa deeply entrenched channel located in a vertical-walled
canyon that in places narrows to less than 50 m. The LCR channel contains runs, riffles, deep
pools and small rapids. Substrates are primarily silt and sand with scattered large boulders. The
LCR is the primary spawning site for endangered HBC in Grand Canyon and is the only known
HBC aggregate in the Colorado River Ecosystem (CRE) from which fish are recruited into the
adult population (Valdez and Rye1199( Coggins and Walters 200'i). Other native fishes,
bluehead sucker (Catostomus disco bolus), flannelmouth sucker (Catostomus latipinnis), and
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speckled dace (Rhinichthys osculus) spawn in the LCR (Robinson et al. 1998) as do exotic
species including channel catfish (Ictalurus punctatus), fathead minnow (Pimephales promelas),
red shiner (Cyprinella lutrensis), and common carp (Cyprinus carpio).
METHODS

Thirteen standardized AGFD hoop nets were fished continuously from April 9 through
May 3,2004, and checked once daily. Hoop nets measured 5 m long and 1m diameter with 6.3
mm mesh, 7 hoops and two throats. Nets were set at 100, 119, 137, 165,420,480,500,577,
675, 1045, 1110, 1160, and 1195 m upstream from the confluence. Net locations were set.as
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close as possible to those used in previous sampling efforts (Brouder and Hoffnagle 1998). Catch
per unit effort was calculated as number of fish caught per hour.

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