Catfish are found on every continent except Antarctica. They
range from fingernail-length miniatures to sedan-length monsters.
They are among the most diverse and common fishes, comprising
one in four freshwater species.
Despite nearly three centuries of exploration and research
and the recognition of more than 2,700 species, an estimated
1,750 catfish species remain unknown to science. But not for
long. Backed by a $4.7 million grant from the National Science
Foundation, scientists at the University of Florida’s
Florida Museum of Natural History have begun leading a five-year
effort to discover and describe all catfish species. The only
one of four similar projects in the NSF’s Planetary
Biodiversity Inventory program that focuses on vertebrates,
the project will tap 230 scientists from around the globe,
with many hauling nets and buckets into some of the world’s
most remote waters. The other NSF projects focus on plants,
insects and microscopic organisms called Eumycetozoa or, more
commonly, slime molds.
CATFISH BREATE AIR AND SQUIGGLE ACROSS LAND. OTHERS
STUN PREY WITH SHOCKS REACHING 400 VOLTS. STILL OTHERS
SUBSIST ON WOOD LIKE TERMITES
above: Pinirampus pirinampu and Phyllonemus typus, below:
Bagre bagre and Pseudacanthicus leopardus
considerations have long forced scientists to limit investigations
to small geographical areas or a few species at a time. The
Planetary Biodiversity Inventory seeks to turn this tradition
on its head, shooting for the discovery and description of
all species within certain groups. Jim Woolley, program director
of the NSF’s biodiversity surveys and inventories program,
says the goal is a comprehensive accounting before it’s
“I think it’s clear to people that we are losing
habitats and losing biodiversity much faster than we can get
a handle on it,” he says. “We want to greatly
stimulate the rate and pace at which species discovery is
being conducted. This program was designed to tackle projects
on a scale never before attempted.”
The University of Florida-led project is headed by Larry Page,
an adjunct curator of fishes at the Florida Museum of Natural
History and principal scientist emeritus at the Illinois Natural
“Larry and the other principal investigators were clearly
in a position to pull this off,” Woolley says. “It
was clear that they had really drawn the community together
and that they were in a position for some very efficient and
The Academy of Natural Sciences in Philadelphia, the California
Academy of Sciences, Auburn University and Cornell University
are the project’s other principal participants.
gets nose to nose with a catfish along guyana's Potaro
By linking scientists and databases via the Internet, the
project will combine modern computer and communications technology
with hands-on collecting expeditions. Page and the other administrators
will distribute small grants, usually no more than $3,000,
to affiliated scientists worldwide for research either on
unclassified specimens housed in museums or on expeditions
to hunt for new species.
Both avenues are expected to bear fruit in the form of peer-reviewed
publications describing new species. Surprisingly, it’s
not always the dustiest museum specimen or most remote waters
that yield the best finds.
Six years ago, Rocio Rodiles was a doctoral student at the
Mexican research institute Eco-Sur working on her thesis research
to inventory all of the fish in the Lacantun River in southern
Mexico near the Guatemala border. The Lacantun is a tributary
of the Usumacinta, which is very well studied because of its
geographic location at the junction of North and Central America.
Rodiles was fishing with hook and line when she reeled in
a large, greenish catfish she had never seen before.
“The first time I saw it, I didn’t know what kind
of catfish it was,” says Rodiles, now a post-doctoral
fellow at the Academy of Natural Sciences in Philadelphia.
The fish looked like it belonged to the ictalurids, the family
of North American catfish, but it had enough unusual features
— such as the large pores on its head — to prompt
Rodiles to take a closer look. When comparisons of the fish
with known species of catfish failed to produce a match, she
contacted University of Texas ichthyologist Dean Hendrickson.
Together, the two discovered other characteristics that seemed
to set the Chiapas fish apart from the ictalurids. For example,
it has six instead of seven or more pelvic fin rays —
the supporting, bony elements of fins — and a very different
pelvic skeletal structure.
Curiously, Rodiles and Hendrickson found that the fish didn’t
fit into any of the South American catfish families, either.
After several years of study and discussion, they and other
icthyologists are now leaning toward placing the catfish in
its own, entirely new family, says John Lundberg, curator
and ichthyology department chair for the Academy of Natural
Sciences of Philadelphia and co-investigator on the catfish
inventory. The catfish has enough evolutionarily primitive
features to suggest that it is only remotely related to North
American catfishes, he adds.
Rodiles’ discovery is unusual, in part because the area
where the fish was found is so well studied and in part because
biologists have already described most large fishes for the
simple reason that they tend to stick out more than others.
Indeed, Rodiles says, the indigenous people who live near
the Lacantun River were familiar with the Chiapas catfish,
which they called “bagre,” as a so-so dinner entrée.
Catfish inventory researchers expect that most new species
they find will not be so distinctive, with some only identifiable
through obscure differences such as the placement of certain
Nevertheless, Lundberg wouldn’t rule out other such
major finds during the inventory. “Most of the new fish
we find will not have a very large body size, and some of
them are going to look like catfish species that we know,
but there’s always a chance of getting something highly
unusual,” he says.
Scientists are planning expeditions in South America, Asia
and Africa, which together are home to the bulk of the world’s
catfish. Destinations include rivers and streams in such forbidding
locales as Angola, Myanmar and Congo.
“The Congo River in Africa is very poorly collected
because it’s very difficult to get in there due to the
civil war, and because of the crocodiles,” Page says.
“But we’re making the contacts there, and we plan
to go in.”
Scientists use several techniques to collect fish specimens.
Probably the most common is netting, with nets ranging from
simple dip nets and large seines that several researchers
haul through the water at once to gill nets. Others include
“electrofishing,” or delivering an electric current
to the water to stun fish to the surface, and line fishing
with trot lines or similar methods. All are used for catfish,
but the fish are often nocturnal, so researchers will often
have to work at night, Lundberg says.
takes teamwork to catch these catfish,
says Larry Page, holding net. Some members disturb
the waters upstream, herding the fish
into the scientists’
Famous University of Florida naturalist Archie Carr was once
quoted saying, “Any damned fool knows a catfish!”
And, indeed, scientists have an advantage in that nearly all
catfish are identifiable by their “whiskers,”
or barbels, their lack of scales and their adipose fin —
the small fin between their dorsal and tail fins. Beyond that,
they are incredibly diverse, incorporating almost every evolutionary
trick in the aquatic species repertoire. Some are armored
against predators. Others, having evolved in caves, are blind.
Some, inhabitants of fast-flowing streams in the Andes and
Himalayas, have modifications to their fins and mouths that
allow them to climb and hang onto vertical surfaces. Many
have venomous spines, which can deliver a painful and sometimes
dangerous toxin to predators or unlucky people. The tiny South
American catfish, the Candiru, which makes its living sucking
blood from the gills of bigger fish, has been known to squeeze
inside the orifices of unfortunate human swimmers.
Such is their diversity and abundance that “they work
as a surrogate for freshwater fishes,” Lundberg says,
explaining that catfish live in so many habitats and display
so many physical and behavioral modifications that they are
good representatives of freshwater fish in general.
all catfish are identifiable by their “whiskers,”
or barbels, their lack of scales and their adipose
fin — the small fin between their dorsal and
tail fins. Beyond that, they are incredibly diverse,
incorporating almost every physical trick in the
aquatic species repertoire.
predate many modern fish. They all belong to the order Siluriformes,
which falls into the biggest and most modern class of fishes,
the bony fishes. The most primitive living bony fishes, sturgeon
and paddlefish, originated in the Jurassic era 225 million
years ago. Catfish appeared well after, with the first fossil
catfish dating to the late Cretaceous about 70 million years
ago. That’s still millions of years before the advent
of most familiar fish such as grouper, members of the most
advanced order of fishes, the Perciformes.
From an evolutionary perspective, catfish have been enormously
successful, branching off into no fewer than 34 families found
in almost every freshwater habitat in the world. Their biodiversity
aside, that’s another reason they’re of interest
to scientists. Since all but a few species are confined to
freshwater, the distribution of the families and species allows
scientists to make inferences about how land masses shifted
over the eons.
“You can conduct biogeographic and other studies important
to understanding biological diversity on a worldwide basis,”
More than two centuries ago, Carl Linnaeus pioneered modern
taxonomy, establishing the now-familiar zoological nomenclature
classing organisms into ever more defined and specific groups
of families, genera and species. Science has experienced unimaginable
transformation since Linnaeus’ era, but his taxonomical
system and the methods behind it have remained remarkably
unchanged. Linnaeus named the first few catfish in his new
system in 1758, including Siluris glanis, the Wels catfish,
Europe’s only native catfish and the world’s largest.
His methods — collection and preservation of the specimens,
careful examination of physical characteristics and comparisons
to similar specimens — will be the same ones used by
the biologists doing the catfish inventory.
At a time when genetics seems to hold the answers to all biological
questions, classic “morphological research” —
comparing the physical characteristics of fishes to determine
their similarities and differences — remains the most
efficient and practical method for new species discovery,
“You can use genetic data, behavior, ecology, but really
it boils down to morphology,” Page says. “The
vast majority of individuals who will work with these fishes
in any context are going to use morphology — they have
to be able to recognize what they have.”
That includes Page, an expert on North American fishes and
author of the Petersen Field Guide to Freshwater Fishes of
North America. For the inventory, he plans to travel to India
this spring to seek new species in Sisoridae, a family of
catfishes restricted to southern Asia.
“When we looked at all the participants in this project
and what they were working on, that catfish family in that
part of the world seemed the most poorly covered,” he
said. “We’re likely to discover a lot of new species.
It’s all going to be new to me, since I’ve never
been to Asia.”
Adjunct Curator, Florida Museum of Natural History
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