7154

• UCREFRP Catalog Number: 7154
• Author: Holden, P. B.
• Title: Habitat Requirements of Juvenile Colorado River Squawfish.
• USFW Year: 1977.
• USFW - Doc Type: FWS/OBS-77/65,
• Copyright Material: NO

INTRODUCTION

The upper Colorado River basin contains two fishes presently listed
as endangered by the U. S. Fish and Wildlife Service, the Colorado squaw-
fish (Ptychocheilus lucius) and the humpback chub (Gila ~). Two
other species, the bony tail chub (Gila elegans) and the razorback sucker
(Xyrauchen texanus), are also rare and are presently being considered
for endangered and threatened status, respectively, The major research
need concerning these rare fishes involves determining their requirements
for subsistence. This information is needed to enhance recovery efforts
of these species and to ensure that future development of natural resources
in the upper basin considers the maintenance of rare fish populations and
thei r habitat.
Two factors appear most important in providing the basis for self-
sustaining populations of the rare fishes: 1) Adequate spawning and rear-
ing habitat, and 2) Interaction with exotic fishes. Areas with reproducing
Colorado squawfish populations, the lower and middle Green River in Utah
(Holden and Stalnaker, 1975), are the least altered large river habitat
in the upper basin. Adult squawfish are found in other areas, but recruit-
ment is lacking (Kidd, 1977), indicating that spawning and rearing require-
ments are not being met in these areas. A determination of spawning and
rearing habitat requirements of both native and exotic species would shed
considerable light on the capabilities of any given river reach to support
these species. The following study was conducted to determine the habitat
requirements of the rare fishes, primarily young Colorado squawfish, as
evidenced by the habitats they use.