A Fish With Finesse
In May of 1911, Ellsworth and Emery Kolb came across
a school of fish at the mouth of the Little Colorado River (LCR), near Beamer’s
Cabin, and wrote:
“...The striking of their tails had caused the noise we had heard. The ‘bony
tail’ were spawning. We had hooks and lines in our packs, and caught all we cared to
use that evening.... They are otherwise known as Gila elegans, or Gila Trout, but
‘bony tail’ describes them very well. The Colorado is full of them; so are many
other muddy streams of the Southwest. They seldom exceed 16 inches in length, and are
silvery white in color. With a small flat head somewhat like a pike, the body swells
behind it to a large hump. Behind the dorsal fin, which is large and strong, the body
tapers down slender and round, ending with a large, strong tail...”
The Kolb’s description and photographs became the first record of one of
the most unique river fishes in the world—but it was not the bonytail (Gila
elegans)! It was the humpback chub, a closely-related species that was not described
until 1946 by Dr. Robert Rush Miller, who also gave it the generic name Gila and
the specific name cypha, which is Greek for “hump-backed” — a
fitting synonym for a fish with a prominent dorsal hump. The humpback chub has been called
unusual, anomalous, bizarre—even grotesque! But the more we learn about this
fascinating fish, the more we learn to appreciate its accomplishments as a species, and
instead use descriptors like beautiful, graceful, and with finesse. The humpback chub is
the fish species that most strikingly characterizes the graceful beauty of the whitewater
canyons of the Colorado River. It is symbolic of how a seemingly harsh and rugged
environment can shape such a thing of splendor.
Manifest Destiny
This first encounter with white European explorers may have spelled
manifest destiny for the humpback chub, having survived 2 million years of torrential
floods, drought, and debris flows in one of the muddiest and most variable rivers in the
world—The Colorado. Can a fish that survived all that nature has been able to
concoct, survive the onslaught of modern technology and the likes of Glen Canyon Dam? No
one really knows for sure, but a handful of scientists with the Glen Canyon Environmental
Studies (GCES) of the Bureau of Reclamation are trying to determine how the dam and the
fish can coexist. These studies began in 1982, and continue to reveal much about a species
that is all but hidden from us by the deep, turbulent, most muddy waters.
Virtually nothing was known about the humpback chub in Grand Canyon before
the completion of Glen Canyon Dam in 1962. Based on a few collections, it is believed that
the species was widespread through Glen and Grand Canyons. It is now confined to one
spawning population in the LCR, primarily because cold water releases from the dam prevent
mainstem spawning. This Grand Canyon population is one of only six in existence; the
others are in the upper Colorado River basin in Black Rocks, Westwater Canyon, Cataract
Canyon, Desolation Canyon, and Yampa Canyon. Populations in Flaming Gorge, Lodore Canyon,
Whirlpool Canyon, Split Mountain, and Debeque Canyon, to name a few, are gone.
Losses of populations and numbers caused the U.S. Fish and Wildlife Service
to classify the humpback chub as “endangered” with protection from the
Endangered Species Act of 1973. GCES since 1982, has added much to understanding the life
history and needs of this unique fish in Grand Canyon. Presently, studies are being
conducted by BIO/WEST, Arizona Game and Fish, U.S. Fish and Wildlife Service, and Arizona
State University, in an effort to recommend to Bureau of Reclamation, dam operations that
will enable the humpback chub and the associated ecosystem, to survive.
Soaring To Greater Depths
The humpback chub is a member of the minnow family (Cyprinidae) with a
maximum size of about 18 inches and 2 1/4 pounds. A distinct, smooth, muscular hump that
rises abruptly behind the head provides the fish with a hydrodynamic stabilizer in swift
currents. Although a relatively weak swimmer, this hump and the large fan-like (falcate)
fins enable it to “soar” in deep roily currents, much like an eagle soars over
mountain cliffs on updrafts and thermals. The humpback chub has finessed its way through 2
million years of existence in the swift whitewater regions of the Colorado River Basin,
where other more powerful fish species have failed in the face of catastrophic floods,
debris flows, high temperatures, and high salinity. Even the strong and more powerful
Colorado squawfish—the “white salmon” of the Colorado River—is
respectful of these swift canyon regions, and tends to use the slower, more gentle river
areas. Not the humpback chub. All known populations, existing or extinct, occurred only in
whitewater regions.
The humpback chub is one of only eight fish species native to the Colorado
River in Grand Canyon. The others are the Colorado squawfish, bonytail, razorback sucker,
roundtail chub, flannelmouth sucker, bluehead sucker, and speckled dace; the first three
are also federally endangered, and the first five are endemic (found in no other river
basin on earth!). This high level of species endemism makes the Colorado River fish
community unique and important to protect. The Colorado River has undergone a long period
of isolation from connection to other river basins, and so, no other river in western
North America has such a high percentage of species that evolved unique to the basin.
Today the humpback chub in Grand Canyon is found primarily in an 8-mile reach
of the Colorado River around the LCR inflow, as well as the lower 8 miles of the LCR in
what appears to be two population components. Adults from the mainstem swim up the LCR to
spawn in April and May. Each female broadcasts up to 3,000 tiny eggs, each the size of a
BB, that hatch after 5 days into minute, transparent larvae less than 1/3 inch long. These
young fish grow about 1 inch per month, and many move into the mainstem in late summer.
Humpback chub mature at about 3 years of age and may live up to 30 years—some of the
fish in the Grand Canyon were probably around before Glen Canyon Dam was built.
Each adult humpback chub spends much of its life in a relatively small area.
Except for spawning migrations, these fish typically move less than 1 mile, and usually
feed in large eddies in mornings and evenings, while remaining in deep pools in the day.
The preferred food of humpback chub in Grand Canyon appears to be freshwater shrimp (Gammarus
lacustris) and blackflies (Simulids), although they will eat a variety of aquatic
and terrestrial insects, seeds, algae, and plant fragments. In the upper basin, they are
known to gorge themselves on the annual migration of Mormon crickets as these locusts move
across the Green and Yampa rivers.
Humpback chub, like most minnows, have no teeth. That is, they have none on
their jaws, tongue, or on their palate, like many other fish. Instead, they have throat
teeth or pharyngeal teeth, which are located on their last gill arch deep in their gullet.
Humpback chub have only two rows of these teeth on each opposing arch (4 and 2 teeth on
each row). These teeth face inward and function as rakers and for tearing food with the
normal swallowing action of the fish. Pharyngeal teeth are replaced regularly like
shark’s teeth, erupting from specialized epithelial tissue instead of from the arch
itself.
Why ‘Study’ These Fish?
GCES scientists in Grand Canyon are trying to determine how the operation
of Glen Canyon Dam affects the food, habitat, reproduction, growth, and survival of the
humpback chub. With no known reproduction in the mainstem, because of cold water
temperatures, it is feared that young chubs hatched in the LCR are fatally
temperature-shocked in the transition from 70oF in the LCR to 45oF in the mainstem. Also,
since fish are cold-blooded (poikilothermic), their growth is slower in colder water.
Removal of sediments in Lake Powell also removes a lot of the original food items carried
by the river, and has changed the kind of food produced in the river. Another area of
research is the impact of non-native fishes such as trout, channel catfish, striped bass,
and other potential predators on survival of the young fish. The eight original native
fishes in Grand Canyon have been overwhelmed in numbers by some 20 non-natives. In other
populations, young humpback chub rely heavily on backwaters for nurseries, but in the
Grand Canyon, the daily fluctuations prevent the permanence of backwaters, and could be
reducing the growth and survival of the young fish. Also, the loss of sand beaches, where
most backwaters form, is also a loss in fish habitat.
The intensive studies in the mainstem Colorado River will wind down after
1993, while work in the LCR will continue through 1995. A long-term monitoring program is
being designed that will mean a greatly reduced effort to follow key features of fish
populations identified through the present GCES studies. For example, status and trends of
fish populations may be monitored by looking at only the very young fish on an annual
basis, and the adults every 3-5 years.
What Good Are They?
The security and well-being of the aquatic ecosystem in Grand Canyon is vital to maintaining the population of humpback chub and the remaining four native fish species. It is likely that this population has been isolated from the other upper basin populations for hundreds or perhaps thousands of years and could be genetically unique. Maintaining the population of humpback chub in Grand Canyon is an important component of Grand Canyon National Park. This and other native species are barometers to ecosystem health, and their decline is a sign that the relationships between the land, water, plants, and animals that took millions of years to evolve, is out of balance. Furthermore, it is clear evidence of a lack of ethics, and a realization that humankind chooses to allow extinction of those life forms which seem insignificant and do not provide immediate and direct economic benefit. Yet, it is prudent to remind ourselves that many medicines were first developed from plants and animals, that radar and sonar were first conceived from understanding bats and dolphins, and that the very concept of flight is based on the wing design of birds. The humpback chub has a highly sensitized lateral line which enables it to feel and locate underwater vibrations caused by a tiny struggling insect in a muddy surrounding, as well as tiny sensory cells on its head known as “neuromasts” that enable this fish to “smell” the unique chemical components of different waters at sensitivities that exceed our instruments. Perhaps these uncanny senses will unveil detection and navigation systems so sophisticated as to render our present technology obsolete, and make all of us realize that value is not limited to present understanding.
What To Do If You Catch One
Humpback chub are commonly caught by fishermen using live bait
(grasshoppers, crickets, earthworms) or artificials (small lures, flies, spinners). They
readily take live bait, salmon eggs, or cheese balls used to catch catfish in deep holes,
or midwater lures and surface flies used to catch trout. Although they are excellent
fighters, anglers are discouraged from fishing for humpback chub. If you catch a humpback
chub, Colorado squawfish, bonytail, or razorback sucker, do not remove it from the water.
Gently, remove the hook and let the fish swim away. If the fish is deeply hooked, gently
handle it in the water or with wet hands, and cut the fishing line even with the
fish’s mouth, and release it. A fish will survive with a hook in its stomach or
mouth, because the hook eventually dissolves.
The penalty for possessing one of these endangered fish—or parts
thereof—is a federal fine of up to $100,000 and one year in jail, as well as a state
fine, which is up to $2,500 and one year in jail, depending on the state where the fish is
caught. If you find a dead fish or parts thereof, that look like an endangered species, we
ask that you place the carcass or parts in a plastic bag and freeze it, if possible, for
immediate transport to a permitted biologist or one of the resource agencies (Game and
Fish, National Park Service, etc.). The above penalty is not imposed under these
conditions, and recovery of these specimens is appreciated. Biologists that work with
these fish in Grand Canyon must possess proper permits from the U.S. Fish and Wildlife
Service, Arizona Game and Fish Department, National Park Service, and the Indian Tribes,
when on reservation lands.
Richard Valdez
BIO/WEST
