7014

• UCREFRP Catalog Number: 7014
• Author: Valdez, R. A. and A. Wasowicz.
• Title: Non-Lethal Stomach Pumping Technique To Recovery Gut Contents of Roundtail Chub ‎(
• USFW Year: 1992.
• Copyright Material: NO

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EXECUTIVE SUMMARY

Forty adult roundtail chub (Gila robusta ), captured by electro fishing from the Colorado River
near the Colorado/Utah state line, were used to evaluate a non-lethal stomach pumping technique for
recovering gut content. Twenty chub were used as the test group and subjected to stomach pumping, and
twenty were examined as the control group. The stomach pumping technique evacuated 100 percent of
the gut ~ontent of all fish treated. No damage to the pharyngeal teeth of any test fish was detected. The
test fish were not anesthetized for stomach pumping, and no short-term ill effects were observed. The
fish were not held for observation of long-term effects. Based on the results of this study, this stomach
pumping technique is recommended for recovering gut content of endangered humpback chub (Gila
0!J2hg) from the Colorado River in Grand Canyon. These two Gila species are closely-related with
nearly identical gut configuration and phyamgeal mill. Food habits analyses of the Grand Canyon
humpback chub are part of the Glen Canyon Environmental Studies.

INTRODUCTION

Backeround

BIO/WEST, Inc. requested permission from the Aquatic Coordination Team (ACf) at its
meeting on December 4, 1990, to use a non-lethal stomach pumping method to recover the gut
contents of humpback chub (Gila~) in Grand Canyon. This proposal was made to satisfy part
of BIO/WEST's contractual requirement to assess resource (food) availability and use for humpback
chub in Grand Canyon and the impact of Glen Canyon Dam. The method was finally tested on
roundtail chub (Gila robusta), a surrogate species. The chronology of events leading to the
conclusion of this testing program is presented in Table 1.

This investigation necessitated sacrificing 40 adult roundtail chub. A study protocol was
established to make maximum use of these specimens. The Colorado Division of Wildlife (CDOW),
U.S. Fish and Wildlife Service (Service), Bureau of Reclamation (Reclamation), and Utah Division
of Wildlife Resources (UDWR) were contacted to inquire about additional uses for these specimens.
Several recommendations were made and implemented. We coordinated capture of these fish with
an ongoing study by Reclamation and The Larval Fish Laboratory of Colorado State University to
determine the effect of electrofishing on native Colorado River fishes. The fish used for this study
were captured with a "typical" electro fishing system used to capture endangered fish in the upper
basin, including a 16-foot tlatbottom aluminum boat, a Coffelt VVP-15, two spherical anodes, and two
cable cathodes. The system was operated at 120 volts, 8 amps, and settings of 30 percent pulse width
and 60 pulses per second. Each fish was observed at capture for external evidence of shock (bruise
marks, spinal deformity, etc.), then placed on dry ice following the stomach pumping process. The
fish were kept frozen for later X-ray examination followed by filleting of the muscle tissue for
assessment of muscle and spinal damage. The results of this study will be reported in a separate
paper when the analyses are complete. Also, scales and otoliths were taken from each specimen to
examine use of these structures for aging this species and perhaps the other closely-related species.
An offer was also made to the Gila Taxonomy Study to make specimens available for tissue
extraction, but we were advised that sufficient material had already been procured from this region
of the Colorado River.

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