9302

• UCREFRP Catalog Number: 9302
• Author: Tyus, H.
• Title: Aquatic Ecosystem Recovery Plan for Mainstream Rivers of the Colorado River Basin.
• USFW Year: 1996.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

EXECUTIVE SUMMARY
Native fishes of the. of a..Siu~er basin are threatened by major
environmental changes that included, but are not limited to alteration of the
hvrirol aic regime and introduction of a.annative$ fishes. All of the "big
river" fishes endemic to the mainstream river ecosystems are in danger, and
70% of the native mainstream fishes are listed as endangered: razorback sucker
Xyrauchen texanus, Caa,q, ado squawfish Ptychocheilus Lucius, h ~~i`fi'a
cypha, and bo ta' G. e)egans. °recovery plans have been written for each of
these endangered species. Other native big river fishes also declining in
abundance and distribution, include the f~annelmouth sucker Catostomus
latipinnis and the roan +?~~ rhub G, robusta, present y candidates for listing
as endangered or threatened.
Most of the endangered Colorado River fishes exist only in remnant
populations. Extant populations of the razorback sucker are found only in
Lake Mohave in the lower Colorado River basin and a two river reaches of the
Upper basin. The Colorado squawfish has been extirpat completely from the
1 ower basin, and i t now occupies only about 80°° of ~ is h~ story c~i 'ange. -"'~- ~ S ~''`~ ~
Humpback chub now exist only in 4 widely-separated canyon habitats. Bonytail ~,JCe~T,
chub, the rarest native fish in the Colorado River, is thoug~it to~exist only
as a few scattered individuals.
The listing of these four fishes and the potential for listing at least
two others from the same mainstream community of big river fishes suggests a
common basis for the endangerment of all species. in fact, the individual
recovery plans for the four fishes describe very similar reasons for declining
populations of the four listed fishes. Alteration of the hydrologic regime,
for example, affects all species in the aquatic ecosystem. There is an urgent
need for solutions directed at the ecosystem level, because there are 12'7
species at risk that occur in, or adjacent to areas designated as critical
habitat. Of these species, 32 are listed or proposed for listing as
endangered (22) or threatened (10), and 95 are candidates for potential
listing.
Aquatic ecosystem protection and restoration are essential for recovery
of the endangered mainstream fishes and will aid in recovery of other species
as well. This ecosystem recovery plan would accomplish this by guiding
recovery efforts for individual species, but not replacing or duplicating
species-specific recovery plans. Management efforts by the Service will
become more efficient with the umbrella approach that the aquatic ecosystem
plan provides, and critical habitat can be managed for the community rather
than separately for each species.
The goal of the plan is to expedite recovery of the listed fishes by
facilitating implementation of existing recovery plans and integrating
recovery planning with critical habitat protection. In addition, because .the
plan seeks remedies to problems at the ecosystem level, it is hoped that it
will also reduce the likelihood of listing additional species that may be at
risk. Main objectives are: (1) to preserve and restore areas of the river
ecosystem by providing natural conditions required for native species, (2) to
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