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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this greater mass of cold water must have remained cooler further down
the river because ambient conditions were not able to raise the water
temperature nearly as fast as it had during the low release period of
1963-1966. Therefore, squawfish reproduction in Dinosaur National
Monument was reduced in about 1967 or 1968 because the Yampa River
could no longer ameliorate the cold inflow of the Green River. Col-
lections of young squawfish the past few years suggest the river does
not return to a normal temperature pattern until it reaches the Jensen
area.

Additional data could be presented to indicate Colorado squawfish
reproductive success in portions of the Upper Colorado basin. Unfortu-
nately no other areas than the two discussed above have more than one
or two years of data. Holden (1973) found young-of-the-year squawfish
to be quite common in the lower Green River in Canyonlands National
Park in 1970 and 1971. He also found yearlings to be quite common be-
tween Ouray and Gray Canyon as well as a few young-of-the-year in 1971.
These data would suggest that squawfish did spawn successfully in much
of the Green River in 1970 and 1971, years of normal flow patterns
(Figures 14 and 15).
As mentioned earlier, Holden (1977) sampled the Jensen-Ouray area
in August, 1977, and also continued downstream to Green River, Utah, in
September. Young-of-the-year squawfish were not found in 1977 between
Ouray and Gray Canyon, but were found at a point about 25 miles upstream
from Green River. This data reinforces the conclusion that 1977 was a
very poor year for Colorado squawfish reproductive success in the Green
River, at least above Gray Canyon (Figure 16).