7152

• UCREFRP Catalog Number: 7152
• Author: Holden, P. B.
• Title: Relationship between Flows in the Yampa River and Success of Rare Fish Populations in the Green River System.
• USFW Year: 1980.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

2

The first hypothesis is supported by data indicating that as areas
of the Colorado River basin have been developed, and as flows are ap-
propriated for out-of-stream activities, these fishes have shown a
reduction in numbers and in SOMe cases have been locally extirpated
(Miller 1961; Minckley and Deacon 1968; Holden et ale 1974; Joseph et ale
1977). This is probably the major reason these fishes are endangered
today. ~'ost of the habitat alteration has occurred in the lower Colorado
basin. There has been some recent speculation that reduced flows are
affecting habitat in the upper basin also, and therefore the last re-
maining populations of these rare fishes (Holden 1979).
The second hypothesis is supported by data collected recently on
Colorado squawfish and is the main topic of this report. The objective
of this study was to determine the relationship between flow in the
Yampa River and reproductive success of Colorado squawfish in the Green
River below the mouth of the Yampa River.

METHODS

The primary analytical approach of this study involved the deter-

mination of which years Colorado squawfish reproduced successfully, and

which years reproductive success was poor, and then a comparison of

flows for those good and bad years. Other factors that ~ay have ac-

counted for low success years, such as temperature, were also noted

although no indepth analysis was made. Two major sets of data are

presented; BIO/WEST data from the Jensen-Ouray area where collections