7327

• UCREFRP Catalog Number: 7327
• Author: Johnson, J. E.
• Title: Status of Endangered and Threatened Fish Species in Colorado.
• USFW Year: 1976.
• USFW - Doc Type: T/N 280,
• Copyright Material: NO

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expenditures. It is, of course, these unique adaptations and a
natural lack of dealing with competition, that are causing their
decline. Most of the large rivers of the Colorado River drainage
are now dammed, and the resulting ponded water above and clear,
cold water below the dams are more suitable to the numerous exotic
species (salmonids, centrarchids, ictalurids, etc.) than the natives.
At least two of the threatened species (Colorado squawfish and hump-
back sucker) and probably also the bonytail chub were well known to
early settlers in Arizona, Utah and Colorado. Large migrations of
these species into smaller tributaries and irrigation ditches in
the spring are well documented, where some were eaten and the sur-
plus pitchforked into fields for fertilizer (Miller, 1961; Minckley,
1973). Within the last 30-40 years, population trends have been
constantly downward, until all four are virtually extinct over the
majority of their range.
Management of these large river, migratory species is complicated
by state boundaries, dams, water demands and other socio-political
problems as well as a lack of knowledge of physical, chemical and
biological parameters needed to sustain them. Most of the suitable
habitats left to these species are anticipated to play an important
role in future energy and water development. If further habitat
degradation occurs, the native Colorado River fish fauna may have
the unique distinction of being the first major fauna to undergo
mass extinction. It may turn out that management of these four
species will be one of the most trying, as well as critical tests
for endangered species legislation in the country, and may con-
tribute to precedent-setting legal decisions. It seems highly
desirable for BLM to begin gathering the necessary information con-
cerning habitat requirements and the availability of these species
immediately, anticipating the potential upcoming conflicting uses
of the waters that make up their habitat.
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