6012

• UCREFRP Catalog Number: 6012
• Author: Miller, W. H., D. L. Archer, H. M. Tyus and K. C. Harper.
• Title: Colorado River Fishery Project
• USFW Year: 1982.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

• ~ a
DISCUSSION
Overview
Over the past 2'~ years, this study has compiled a vast amount of
new biological information on the endangered Colorado River fishes. We
have determined the distribution and identified key critical areas in
the Upper Colorado River Basin.
Generally, it appears that the bonytail chub is near extinction in
the upper basin with only one isolated area near Coal Creek in the Green
River where this species can now be taken. The humpback chub has three
populations in the upper basin; one remnant, poorly defined population
in the Green River in the Coal Creek area and two rather secure populations
in the main Colorado River at Black Rocks and Westwa-ter near the Utah-
Colorado state line. The Colorado squawfish occurs throughout the upper
basin, but depends on a few key areas for spawning and fry rearing. Key
spawning areas in the Green River drainage are the lower Yampa down to
Split Mountain on the Green River and in Gray Canyon on the lower Green
River. Key spawning areas in the Colorado River are from Loma to the
Utah state line. Fry rearing areas are downstream from spawning areas
and are characterized by shallow depths with side channels and backwater
habitat.
Life history information gathered has documented the rather sed-
entary, isolated existence of the humpback chub populations. Conversely,
for the squawfish our data indicates a wide ranging species capable of
movements over great distances, with a homing behavior and some exten-
sive use of tributary streams.
Overall, it appears that we need
dangered Colorado River fishes to the
is probably decreasing in population,
of management. Whereas, the humpback
the isolated habitats where they now
rivers do not deteriorate further.
to key our management of the en-
Colorado squawfish. This species
but still offers the possibility
chub are believed to be secure in
reside if habitat conditions in the
Recommendations
Recommendation of river flows needed for each target species were
made based upon what was needed for survival of the species at the
present population level. Recommendations are limited to the main Green
and Colorado Rivers and are specific to representative reaches of the.
river. It should be pointed out that flows provided at upstream stations
of the main Green and Colorado Rivers are assumed will remain in the
respective rivers and provide all or a aajor portion of the flows needed
at down river locations.
Flow needs for each target fish species were based upon a sequence
of evaluations and determinations. The following determination or
evaluation was made for each target species: Z) Where were the critical
geographic areas in the river system, 2) What was the critical life