7144

• UCREFRP Catalog Number: 7144
• Author: Inslee, T. D.
• Title: Spawning and Hatching of the Razorback Sucker
• USFW Year: 1982
• USFW - Doc Type: Western Association of Fish & Game Agencies
• Copyright Material: NO

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Probably the greatest potential impact is the indirect effect of
withdrawing water from the Green River system. The 30 cfs proposed for
withdrawal should not be a noticeable quantity, even during low flow
periods, by itself. But the cumulative impact of a number of small
withdrawals could pose serious problems. As mentioned above, and
presented by Holden (1977), Colorado squawfish reproductive success
in the Green River was very poor in 1977. The major factor hypothesized
to account for this phenomenon is the reduced flows of the Yampa and
White rivers due to a drought that year. This suggests very strongly
that Colorado squawfish have a minimum flow requirement below which
reproductive success is very poor. The actual causative agent, such
as water volume, water velocity, available habitat, or altered temper-
ature regime, is not known. Holden (1977) hypothesized that altered
habitat may have been the problem, and noted that daily fluctuations
due to releases from Flaming Gorge Dam were quite large (.5 m) near
Jensen. Fluctuations in late 1979 were not nearly the size of those
in 1977, averaging only about 0.2 m. Fewer backwaters that did not
change daily due to river level were available in 1977 than 1979.
Therefore, if flows are reduced in the Green River beyond a point
that is as yet undetermined, the best remaining naturally reproducing
population of Colorado squawfish could be seriously impacted. It should
be stressed again that this impact could be caused by the cumulative
effect of a number of small withdrawals from the Green River and its
tributaries, of which the subject withdrawal is only one.