Colorado State University Researcher's Detective Work Uncovers Clues To Save West's Endangered Fish
Thursday, May 22, 1997
FORT COLLINS--A Colorado State University researcher's
uncanny ability to identify young fish smaller than the tip
of a pencil is helping to restore populations of endangered
fish in Colorado and the West.
Relying on keen eyesight, a microscope and 30 years of
experience, Darrel Snyder is one of a handful of people in
the world who can identify days-old fish so small most
people wouldn't see them darting around rocks at the edge of
a stream.
Snyder and his associates already have identified the
larvae of endangered fish in reaches of the Upper Colorado
River Basin where they were not previously thought to
reproduce. This signals the possibility that other spawning
sites of endangered fish may exist but have gone undetected.
The researcher's knack for identifying fish provides
state and federal fishery management agencies with important
clues useful in efforts to monitor and bolster populations
of endangered razorback sucker, Colorado squawfish, bonytail
and humpback chub in the upper basin. The basin stretches
from the high mountains of Wyoming and Colorado, through
Utah and New Mexico, to Lee's Ferry below Lake Powell in
Arizona.
"Everything we need to know about the survival of these
threatened species begins when the fish are days old," said
Snyder, a fish larvae taxonomist at Colorado State's Larval
Fish Laboratory. "Without that knowledge, it's difficult to
predict where they have the best chance for survival or
analyze what kind of habitat is ideal for producing
offspring."
The Colorado State researcher helped prove that
razorback sucker are reproducing in parts of the Green River
in Utah where they previously weren't known to spawn. Snyder
also has confirmed a small population of Colorado squawfish
are successfully reproducing in the Gunnison River in
Western Colorado. It was the first time squawfish larvae
were discovered upstream of the Redlands Dam between Grand
Junction and Delta, a discovery that points to the likely
success of a recently installed fish ladder which allows
migrating adults to swim around the dam to spawn upstream.
Snyder likens his work to that of a detective. State
and federal fish management agencies send the lab tens of
thousands of larval and early juvenile fish each year in
samples collected from upper basin rivers and tributaries in
Colorado and Utah. Then, Snyder and his assistants begin the
tedious process of sorting the tiny fish into smaller lots
by species with the help of microscopes.
"It's a lot like trying to solve a crime," said Snyder,
who estimates he's seen millions of young fish through the
lens of a microscope. "You look for the clues and piece them
all together to come up with the answer. Sometimes, the
answer is elusive."
To the untrained eye, fish larvae resemble pale white
tadpoles ranging between one-eighth inch and one inch in
length and lack the many distinctive features that make
identification of adult fish easy. An additional challenge
is that larvae of one species can look strikingly similar to
different species at various stages of development. In order
to identify fish larvae accurately, Snyder must know what
each species looks like at every stage of growth--which
means hundreds of different possibilities.
Another difficulty is the limited references available
to identify fish larvae. Snyder estimates that only one-
quarter of North America's freshwater fish species have been
adequately described as larvae for identification purposes.
Due in part to the efforts of Snyder and his associates,
nearly two-thirds of the fish larvae in Colorado have been
described.
In the case of fish larvae identification, Snyder looks
for a variety of clues such as pigmentation, the number of
muscular body segments, position of various physical
structures, overall size and skeletal development. By
analyzing those features, Snyder can differentiate between a
recently hatched razorback sucker and its close relative--
the flannelmouth sucker--with ease. When specimens are too
similar or damaged to make visual identification,
researchers sometimes turn to DNA analysis for a definitive
answer.
"When all else fails, I just look for their name tags,"
Snyder jokes.
The lab's efforts at Colorado State are an important
part of the Colorado River Recovery Program, a 15-year
project directed by the U.S. Fish and Wildlife Service and
state agencies in Colorado, Wyoming and Utah. The program
aims to restore declining populations of fish native to the
Upper Colorado River Basin.
Over the past 60 years, the number of many native fish
in the upper basin has dropped dramatically, largely due to
the introduction of non-native sport fish and changes in
habitat caused by dams.
Snyder said past research focused only on how adult
fish fared in these waters. With the revelation of criteria
to identify fish larvae, the focus shifted toward work on
early life stages. Researchers now are better able to
monitor where reproduction takes place and investigate how
changes in habitat, water quality or non-native fish affect
larvae and juveniles.
Research at the larval lab has showed that many factors
influence the survival rates of young fish, such as the
availability of backwaters in rivers, water temperature,
dissolved oxygen levels, food supply and predation by other
fish. That's where Snyder fits in.
"Darrel can identify fish for us at these early ages,
which is key to helping us understand their development,
habitat requirements and survival," said Robert Muth,
director of the Larval Fish Lab. "A large part of the
research we do to help these endangered fish couldn't be
done without his expertise."
Researchers from many parts of the United States and
Canada consult with Snyder or send him specimens for
identification, verification and sometimes formal
description. He's described the larvae of many fish,
including four of North America's seven sturgeon species.
The lab, one of the few in the world that focuses on
identifying freshwater fish at early stages of life, was
established in 1978. Once fish are identified, most
preserved specimens are counted, measured and stored for
future study or reference. Over 3 million fish are in
storage.
Some specimens are dissected to study food habits.
Small ear bones--called otoliths--are removed from other
fish to determine age, growth rates and probable spawning
dates based on the bones' daily growth rings, which are
similar to the annual rings of trees. Larval Fish Laboratory
researchers and students also study fish behavior, determine
the effects of toxic chemicals and electric currents on
fish, track adult fish migration patterns with
radiotelemetry and conduct other field and laboratory
research related primarily to endangered species.
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