Western Pennsylvania waterways may be the source and
the destination for non-native fish, and that has the
potential to disrupt ecosystems in their new environment.
Flathead catfish, including several young, have been
caught below the Safe Harbor Dam on the lower Susquehanna
River this summer. Since 1997, flatheads have also been
caught in the Delaware and Schuylkill rivers, and in the
Blue Marsh Reservoir, all in eastern Pennsylvania.
The species is not native to eastern Pennsylvania, but
it is a natural inhabitant of the Ohio River drainage,
including the Allegheny and Monongahela rivers in Western
Pennsylvania. Flatheads have been known to reach 100 pounds
and are active predators. The Pennsylvania state record
is more than 40 pounds.
It is not known how the flathead catfish became established
in rivers in eastern Pennsylvania, but there is concern
that its arrival could harm established fisheries there.
Where the diets of flatheads have been studied, sunfish,
other catfish and crayfish are principal prey items.
Flatheads could disrupt native fisheries both by competing
with native fish for food, and by eating native fish directly.
In the Cape Fear River in North Carolina, where the flathead
has also been introduced, researchers documented a severe
decline in native fish populations within 15 years after
flathead catfish became established there. Scientists
found that after the flatheads had decimated populations
of sunfish and other catfishes, they switched to feeding
on shad.
That could prove serious on the Susquehanna, where the
Fish and Boat Commission has led a cooperative program
to re-establish a population of American shad in the river.
Shad were abundant in the Susquehanna until early in the
1900s and supported a vibrant commercial fishing industry.
Flathead catfish could hinder the reintroduction effort
and the 500,000 angler-per-day annual sport fishing the
Commission estimates would result.
Mike Kaufman, a Fish and Boat Commission biologist,
said, "We're going to start spreading the word that we
would like anglers to keep and kill all flathead catfish
caught near Safe Harbor Dam on the Susquehanna."
Commission press spokesman Dan Tredinnick added another
perspective.
"The flathead is an opportunistic feeder," he said.
"If they get the chance, they will take shad. But smallmouth
bass [another introduced species in the Susquehanna] love
shad also, and at the right time of year a shad imitation
is the best lure for smallmouth. We don't necessarily
see this as the end to the shad reintroduction."
Flathead catfish are olive to light brown in color,
with dark brown to black mottling. They have a wide head
that appears flat and depressed, with chin barbels colored
white to yellow. Unlike the more common channel catfish,
the tail is not forked and it may appear square or rounded.
The best identifying mark is the lower jaw, which protrudes
beyond the upper jaw.
According to the Fish and Boat Commission, anglers in
Western Pennsylvania should consider the flathead a desirable
game fish. In the Ohio drainage, where it has lived for
centuries, the flathead poses no threat to native fisheries.
Not so with the bighead carp, which some biologists
believe they have spotted recently in Lake Erie. The bighead
carp is a native of lowland rivers in eastern China, but
has been imported, hatched and raised in hatcheries in
the American South. Commercial catfish farmers stock bighead
carp in catfish ponds to rid the impoundments of algae,
phytoplankton and other undesirable plants. Some fish
have escaped and become established in rivers from Alabama
northward to the Ohio, Missouri, and upper Mississippi
rivers.
Bigheads have grown to 60 pounds in American rivers
and 90-pound specimens are not uncommon in Asia. The fish
have also been spotted in a canal linking Lake Michigan
to the Illinois River, a tributary of the Mississippi.
Biologists believe this could be the route the bigheads
used to access the Great Lakes. As with the flathead catfish
and American shad in the Susquehanna, the bighead carp
could threaten efforts to reintroduce the native paddlefish
into the Ohio River in Western Pennsylvania. As a "filter
feeder," combing large amounts of plankton and organic
debris from the water as a food source, the bighead competes
with the native paddlefish for nourishment.
Dr. William Kimmel, an aquatic ecologist at California
University of Pennsylvania, is doing research on the paddlefish
reintroduction effort on the Ohio River.
"These [bighead carp] have been reported 25 miles from
Chicago and from the Ohio River near Wheeling," Kimmel
said. "If their food habits include zooplankton at any
stage in their life cycles, they could threaten not only
paddlefish but larval fishes of many species, posing a
threat to the entire river food chain including popular
game species."
