Dr. Tom Kwak, 919/513-2695
Kulikowski, News Services, 919/515-3470
1 , 2002
Flathead Catfish a Danger to Native N.C. Fish Species
love the flathead catfish because it's big, it puts
up a good fight and it tastes good.
But the flathead has a dark side: It needs to
eat living fish, and lots of them. This attribute
has fisheries and wildlife officials worried about
some native North Carolina fish species, including
the redbreast sunfish, white catfish and bullhead
species, and small madtoms, which have all seen
a population decline in areas where the flathead
has been introduced. This trend is also causing
concern in other states along the Eastern Seaboard,
all the way from Florida to Pennsylvania.
Tom Kwak, associate professor of zoology
at North Carolina State University and unit leader
of the N.C.
Cooperative Fish and Wildlife Research Unit,
is the principal investigator of one of the first
extensive studies of the flathead catfish. The
N.C. Cooperative Fish and Wildlife Research Unit
is a partnership of the U.S.
Geological Survey, the N.C.
Wildlife Resources Commission, NC
State University and the Wildlife
student Bill Pine shows off a 45-pound flathead
catfish caught in eastern North Carolina waters.
catfish are not native to North Carolina, Kwak says;
the species was introduced in the state in the mid-1960s
as a sport fish. Little did N.C. officials know back
then that the flathead, which seems to get along well
with other fish in its natural habitat - the Mississippi
River and its tributaries from Minnesota to the Gulf
of Mexico - would put its carnivorous traits to use
in harmful ways.
flathead catfish is unique among American catfish in
that it is an obligate carnivore - it must eat living
fishes or other living invertebrates like crabs or crayfish,"
Kwak said. "It won't eat plants or other dead material,
and you can't catch it with popular catfish baits like
cheese or chicken liver."
And it needs a lot of live fish to grow, Kwak says.
To gain one pound, flatheads must eat about 10 pounds
of live food. That adds up to a feeding frenzy when
you consider that the largest flathead captured in North
Carolina tipped the scales at 69 pounds, and the world
record is a 127-pounder caught in Kansas.
Kwak's cooperative unit was called in when biologists
from the N.C. Wildlife Resources Commission noted that
the numbers of native N.C. species began showing declines
in areas inhabited by flathead catfish. His team joined
Wildlife Commission biologists to determine if there
is merit to the theory that the presence of flatheads
leads to reduced numbers of native species like redbreast
sunfish and other types of catfish, and also to discover
how these fish behave and what types of habitats they
use in North Carolina rivers.
To learn more about the flathead catfish, the team -
which includes NC State zoology faculty Dr. James Rice,
Dr. Richard Noble, Dr. Joseph Hightower, doctoral student
Bill Pine, research associate Scott Waters and a number
of NC State graduate and undergraduate students - studies
flathead populations in three eastern North Carolina
rivers: the Northeast Cape Fear River near Burgaw, Contentnea
Creek near Kinston and the Lumber River outside Lumberton.
team's focus is on three objectives: to ascertain approximate
numbers of flathead catfish, along with other population
characteristics like size and growth rates; to gauge
the behavior and migration patterns of flatheads; and
to determine the predator-prey relationship between
flatheads and other fish.
accomplish these goals, the researchers collect flathead
catfish by electrofishing - that is, generating low
frequency electrical current in the water and then catching
the stunned flatheads as they float to the surface.
Researchers then measure and weigh each fish; mark all
fish with small computer chips called passive integrated
transponder tags that each have a unique number; and
pump the stomachs of the fish to determine the fish's
diet. A select number of flatheads - at least 12 in
each of the three areas studied - also have a radio
transmitter implanted so researchers can track movement
Some of the research findings have been surprising,
Kwak and Pine say. It appears that the flathead catfish
is thriving, but acting differently, in its non-native
North Carolina environment.
Flathead densities in the Neuse River system are greater
than those reported in its native Mississippi River
basin, the researchers say. Moreover, many flatheads
migrate further than previously expected.
on one study in tributaries of the Mississippi River,
it was assumed that in the flatheads stayed within one
mile of where they were found," Kwak says. "In
North Carolina, many are moving a lot, sometimes up
to 30 and 40 miles of where they were originally found.
This has serious management implications because flatheads
are not just isolated in small areas, but moving throughout
an entire river basin."
The study also shows that flatheads are frequently found
in deep holes in the river, especially habitats with
cover, such as log piles or other woody debris.
Stomach content analysis shows that flatheads consume
a wide variety of prey items, including sunfish, crayfish,
and occasionally shrimp and small crabs, Pine says.
The flathead was recently spotted in the upper Cape
Fear River, raising fears that a rare, endangered fish
native to that river, the cape fear shiner, could be
in trouble. Kwak and other NC State researchers and
students are currently conducting habitat studies on
the cape fear shiner, and may eventually examine the
relationship between this small minnow and the flathead.
Kwak has two suggestions to control the flathead population
in the state. "Anglers should definitely practice
catch-and-keep when they get a flathead catfish,"
he said. "And while it's illegal to move fish around
from one river to another, someone moved the flathead
into the upper Cape Fear. You're not doing anyone any
favors by introducing the flathead into new waters;
it's destructive to our native fisheries, and it's irresponsible."
The information gained in this research will help state
biologists work together with the public to manage fisheries
to protect the state's native natural heritage. The
final report on the impacts of flathead catfish in North
Carolina will be released next summer.