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Last modified
7/14/2009 5:02:31 PM
Creation date
5/20/2009 10:51:21 AM
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UCREFRP
UCREFRP Catalog Number
7868
Author
Kidd, G. T.
Title
Endangered Fish Of The Upper Colorado River, Observations From 1970 Through 1995.
USFW Year
1996.
USFW - Doc Type
\
Copyright Material
NO
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It is generally assumed that the installation of the irrigation diversions and removal of water from <br />the Colorado River have been the primary cause for the decline of razorback sucker and Colorado <br />squawfish populations (USFWS, 1993). Mr. Kidd agrees that removal of water from the Upper <br />Colorado River system probably has resulted in a decrease in available fish habitat as compared <br />to the pre-1900s condition, and has resulted in the irrevocable alteration of the hydrologic <br />dynamics of the Colorado River. However, he also believes that two other major factors were <br />at least as important in causing the decline of the endangered native fish: <br />1. Physical changes to the river including: channelizing, bank armoring, alteration of <br />river dynamics, and channel changes due to flooding have resulted in the loss of <br />almost all spawning and rearing habitat. <br />2. The introduction and proliferation of non-native fish have resulted in the loss of <br />native fish eggs and embryo fish from predation. Non-native fish presently dominate <br />all remaining backwater areas. <br />While the flow regime of the Upper Colorado River has not significantly changed since 1975, the <br />endangered native fish populations have seriously declined. This may in part be due to a long- <br />term, gradual decline of the species as a result of water depletion from the river, and impeded <br />migration from diversion structures; however, the other factors are probably at least as important, <br />and in the case of the razorback sucker, much more important. <br />Mr. Kidd's ideas are supported by his observations of the razorback sucker decline in the river <br />reach between the Government Highline Canal diversion upstream to the Town of DeBeque. This <br />reach of the river has not been subject to major irrigation diversions as it is downstream of the <br />major diversion structures. Prior to 1974, razorback suckers were common in this reach, despite <br />having been isolated from the downstream populations by the diversion structures for more than <br />60 years. As stated previously, razorbacks were observed spawning and evidence of recruitment <br />was present until the mid-1970s when the following events took place. In 1974, one major <br />spawning area, the Mesa County DeBeque gravel pit, was mined and was lost to use by the <br />9427SREPORTMMWPP-C.W WE 9
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