7112

• UCREFRP Catalog Number: 7112
• Author: Minckley, C. O.
• Title: Fishes of Arizona.
• USFW Year: 1973.
• USFW - Doc Type: Arizona State University,
• Copyright Material: YES

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At one extreme the large, through-flowing Colorado River provided
an impressive, special fish habitat prior to damming. This river was
highly turbid, strongly-flowing, swift and turbulent, and on the other
' hand subject to long periods of low flow during drought (Sykes, 1937;
Miller, ] 961 b). Almost all physical and chemical conditions of the
primitive river must have fluctuated quickly and radically, and a special
fish fauna, which is to be detailed later, had become adapted to its
vagaries. Damming results in relative stabilization of many features of
any riverine environment (Moffett, 1949; Neel, 1963; Vanicek, et el.,
1970). Temperatures become colder in summer since water is released
+ from the depths of reservoirs for generation of power or other down-
stream uses; winter temperatures become relatively warmer and more
~ stable. Turbidities decline since silts and debris become deposited in the
quiet waters above dams. Chemical conditions become stabilized because -
of mixing and other phenomena in the upstream lakes. Despite such
changes, the Colorado River remains an exceedingly unique habitat in its
more inaccessible and unimpounded segments in the state (Fig• i), but
none of the stream may be considered undisturbed or pristine.
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+ Fi ure 1. Colorado Rive - ~ - ~ . ~ ~ .
8 r mainstreom in Grand Canyon National Park, Ariaona.