7336

• UCREFRP Catalog Number: 7336
• Author: Valdez, R. A. and B. C. Nilson.
• Title: Radiotelemetry as a Means of Assessing Movement and Habitat Selection of Humpback Chub.
• USFW Year: 1982.
• USFW - Doc Type: Grand Junction, Colorado.
• Copyright Material: YES

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RADIOTELEMETRY AS A MEANS OF ASSESSING
MOVEMENT AND HABITAT SELECTION
OF HUMPBACK CHUB

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By

R.A. Valdez and B.C. Nilson
U.S. Fish and Wildlife Service
Grand Junction, Colorado 81501

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ABSTRACT

Eight endangered humpback chub were captured, equipped with
AVM/SM-l internal radio transmitters, and released in the Black
Rocks area of the upper Colorado River to aid in assessing mOve-
ment, habitat selection, and spawning sites for the species. The
fish were tagged and released in two lots of four each on 3 May
and- 30 May 1981, and monitored for periods of 4-93 days. Average
movement per fish for the period monitored was 0.8 km (0-3.7),
compared to 1.6 km (0-23.0) for fish equipped with plastic Carlin
tags for a period of up to 434 days. Three of the eight radio-
tagged fish returned to their original capture location suggesting
a homing behavior and a tendency for the species to remain in re-
stricted regions of the river. These fish also exhibited patterned
diurnal and nocturnal vertical movements, generally occupying
shallow shorelines at dawn and evening, deeper water in mid-
morning and midafternoon, and the deep midchannel at midnight and
midday. Radio-tagged humpback chub in Black Rocks occup~ed
depths of 0.7-15.2 m (x = 4.7). They occupied velocities
of 0.2-1.3 fps (x = 0.6), and primarily sand and bedrock sub-
strates. This habitat section was similar to that associated with
humpback chub in Black Rocks captured by electrofishing or en-
tanglement nets. Reception of fish modules in water deeper than
6 m was irregular and restricted habitat information in the
deeper water. This investigation demonstrated the feasibility of
radiotelemetry with humpback chub, but there is a need for small
but stronger fish modules.

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INTRODUCTION

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Radiotelemetry was used by the Colorado River Fishery Project (CRFP)
to supplement information on movement, habitat selection and spawning sites
of humpback chub (Gila cypha) in the upper Colorado River. The investigation
was conducted in the Black Rocks area of Ruby Canyon, Colorado, 7 km up-
stream from the Utah state line. Black Rocks supports one of the three
largest concentrations of humpback chub in the Colorado River system (Valdez
and Clemmer 1982).

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