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

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of fish presented in this report, each year's sampling will be noted
(effort) and the level of success for that year indicated.
Flows to compare with the fish data were obtained from USGS
gauging data. The gauge at Jensen, Utah, on the Green River in Dinosaur
National Monument near the mouth of Split Mountain, describes the flow
from the mouth of the Yampa River to Ouray. The gauge at Greendale,
Utah, depicts the flow in the Green River between Flaming Gorge Dam and
the mouth of the Yampa River. The only inflow between these gauges of
any consequence is the Yampa River. Therefore, the difference between
the Jensen and Greendale values was considered to be the Yampa's input.
The hydrographs used to depict the flow are nothing more than
graphs of the daily flow at the gauge in question. The time period
March-August was used because this is the flow period which generally
shows the greatest change and also is the period leading up to and in-
cluding spawning of Colorado squawfish.

RESULTS AND DISCUSSION

Colorado squawfish are America's largest minnow, apparently
reaching lengths of 6 feet and weights of 80-100 pounds at one time.
Adults are long-lived, reaching sexual maturity at about 7 years of
age (Vanicek and Kramer 1969). Spawning occurs in the summer at river
temperatures of near 700 F (Holden and Stalnaker 1975). Young prefer
quiet backwaters, where they initially feed on small crustaceans. As
they grow older, and larger, they begin to eat larger insects and fish.