7378

• UCREFRP Catalog Number: 7378
• Author: Wydoski, R. S.
• Title: Potential Impacts of Alterations in Streamflow and Water Quality on Fish and Macroinvertebrates in the Upper Colorado River Basin.
• USFW Year: 1980.
• USFW - Doc Type: 77-147
• Copyright Material: YES

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data are available to evaluate parasitism as a cause for the decline of

native species in the upper basin. but this possibility cannot be dis.
counted,

If fish populations decline until the species is considered threat-

ened or endangered. genetic diversity of the species may be changed to

the degree that genetic heterozygosity is decreased or lost, This ge-
netic heterozygosity allows the fish to adapt to various environmental

conditions and. if lost. may accelerate the extinction of the species.

Recently. Smith and coauthors (1976) have pointed out the importance

of population genetics in the management of all fish and wildlife popu.

lations. and their concern is especially applicable to threatened or

endangered species that are found in the Upper Colorado River Basin.

The expected distribution of fish by generalized ecotypes in the

Colorado River Basin has been outlined by Bishop and Porcella (in this

volume). This distribution is divided into high-elevation trout waters

(>5.000 ft,). transition reaches that contain trout and other species,

and meandering stretches with lower velocities and warmer water tempera-

tures that contain the endemic species and introduced species such as

channel catfish. Ictalurus punctatus; carp. Cyprinus carpio; and creek

chub. Semotilus atromaculatus,

:h

Changes Caused by Impoundments

The cold. clear. headwater streams of the Upper Colorado River

originate in the Rocky and Uinta mountains, The main tributaries of

the river drop into a dry desert. where spectacular canyons have been

carved out over the years. Here the river has been historically warm