7908

• UCREFRP Catalog Number: 7908
• Author: Valdez, R. A. and R. J. Ryel.
• Title: Life History and Ecology of the Humpback Chub ‎(
• USFW Year: 1995.
• Copyright Material: NO

PREFACE

Nearly one million people a year visit Grand Canyon
National Park. ~ost come to peer into the depths of
the canyon to catch a gli..-npse of the thin watery
ribbon of the Colorado River nearly 1 mile below
the canyon rim. And many, over 20,000 people
annually, come to raft the world-renowned
whitewater marked by 160 recognized rapids in 225
miles of largely inaccessible wilderness. Despite the
many people who visit or know of the Grand
C anyon, few recognize or understand the fishes
that live in this ancient desert river.

The Colorado River and surrounding arid landscape
hardly seem a fitting place for fish. Yet, the very
nature of this violent, muddy, and saline river has
given rise over nearly 3 million years to one of the
most unique and highly indigenous fish assemblages
in North America. Of 35 fish species native to the
Colorado River Basin., 26 (74%) are endemic, or
found in no other basin on earth. Until recently,
when the names of these fishes began appearing in
news articles and environmental reports, the fishes
of the Colorado River and Grand Canyon were
known primarily to ichthyologists, and their role and
importance in the ecosystem were not well
understood.

Native Americans and early explorers used the
fishes of the Colorado River as a food source, but
the inaccessible and treacherous river made
widespread use of the fish impractical. More
recently, anglers considered them "trash fish", and
they were poisoned by resource agencies to make
room for introduced trout and other game fishes.
Federal protection for these fish (i.e., Endangered
Species Act of 1973) brought to the attention of the
public the decline of these unique life forms and the
plight of this ancient and overused western river.
Protection for the bonytail, roundtail chub, and
Colorado squawfish--largest of North American
minnows at 100 pounds! --came too late in Grand
Canyon, where the species were extirpated by the
early 1970s. It may also be too late for the
razorback sucker, a species that is now very rare in
the region. Declining numbers of tlannelmouth
suckers and bluehead suckers also warn of
impending and persistent threats to these native
species. Only the speckled dace seems to be
widespread., although its numbers may also be
declining. .

Many people think of the Colorado River fishes as
channel catfish in muddy waters or rainbow trout in
cold, clear tailwaters below dams. While these
introduced species are valuable game fishes, they
often compete with or prey upon the nativ.e forms.
Hence, the dozen or so alien species that inhabit the
river are also an important aspect of the present
aquatic ecosystem, and these species are important
considerations in achieving a balanced approach to
river management.

While the emphasis of this report is on the
humpback chub, the decline of all the Colorado
River native fishes serves as a reminder of the
connectivity between all life forms and the need to
protect ecosystems. Aldo Leopold (1949) best
described the relationship:

"The outstanding scientific discovery of the
twentieth century is not television. or radio. but
rather the complexity of the land organism. Only
those who know the most about it can appreciate
how little is known about it. The last word in
ignorance is the man who says of an animal or
plant: 'What good is it?' If the land mechanism as
a whole is good, then every part is good. whether
we understand it or not. If the biota. in the course
of aeons, has built something we like but do not
understand. then who but a fool would discard
seemingly useless parts? To keep every cog and
wheel is the first precaution of inteJiigent
tinkering. "

The aquatic ecosystem of the Colorado River has
been dramatically altered since the late l800s.
Many aspects of the historic structure and function
of the system have been modified or eliminated.
While recovery of the pre-1800s condition is not
possible, preservation of some historic structure and
function is possible and essential to preservation of
native fishes and maintenance of a balance
native/non-native fish assemblage.

Although this report focuses on the humpback chub,
we advocate development of a fish management
plan that considers the existing native fish
assemblage (humpback chub, razorback sucker,
tlannelmouth sucker, bluehead sucker, speckled
dace), extirpated native species (Colorado
squawfish. bonytail, roundtail chub), and numerous