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Walking
Catfish Not As Bad For Florida As Once Thought
NEIL SANTANIELLO
Associated Press
Posted on Sun, Jan. 16, 2005
South Florida Sun-Sentinel
FORT LAUDERDALE, Fla. - The walking catfish sent unsettling
ripples through Florida after surfacing on a north Broward County angler's
hook in 1967.
The discovery of that exotic fish, capable of undulating briefly over land
with its stiffened pectoral fins and a body-rocking motion, spurred
projections that the species would dominate, and perhaps seriously harm,
native Florida fish populations.
Thirty-seven years later, that Frankenfish fear has yet to pan out, said
Paul Shafland, director of the Florida Fish and Wildlife Conservation
Commission's Non-Native Fish Research Lab in Boca Raton.
"It's certainly not had any of the catastrophic effects originally
associated with its find in Florida," he said. "However we still consider
it problematic. We wish it weren't here."
The walking catfish, Clarias batrachus, breathes air, and can make short
migrations across land, which it sometimes does after rains leave standing
water and soggy landscapes. While other exotic fish live sub-surface
lives, the south Asian native's land locomotion brought it headlines.
"People saw a fish out of water, and it just had a lot of sensationalism
attached to it," Shafland said.
The catfish covered a lot of ground rather quickly once it got a foothold
outdoors. It has spread, via
interconnecting canals and other means, from
the first catch west of Deerfield Beach north to Walt Disney's Magic
Kingdom, where a worker recently snagged one, said Walt Courtenay,
fisheries research biologists for the U.S. Geological Survey.
One of 34 exotic fish existing in Florida, the walking catfish remains
widespread and "locally abundant," Shafland said. It fanned out across 20
counties in just 10 years, according to the Florida Museum of Natural
History.
But scientists said its numbers appear to have declined in the 1980s and
1990s after an initial population boom.
"We've seen that with a lot of introduced fishes," said Bill Loftus, a
Geological Survey research ecologist based at Everglades National Park.
Predators eventually start to key in on them, food dwindles and their
proliferation is curbed, he said.
"They don't really crash - they come to a kind of balance with the
environment," Loftus said.
The lack of a visibly serious impact from walking catfish does suggest
that "the aquatic ecosystem is far more resilient to disturbances than
what is commonly perceived by environmentalists," Shafland said.
A 1970 Smithsonian Contributions to Zoology article described the walking
catfish's foray into Florida as possibly "the most harmful introduction to
any North American area so far witnessed," Shafland noted. A state exotic
fish research leader in 1968 called the walking catfish "a monster."
Shafland thinks the thus far innocuous fate of the walking catfish should
temper fear generated by more recent exotic fish finds in South Florida -
the discovery of the Asian swamp eel on the Broward-Miami-Dade County line
in 1998, and the bullseye snakehead in Sunrise in 2000. The latter is a
relative of the toothy northern snakehead from China, which can survive
out of water for days and was dubbed the fish "from Hell" in news reports
after being hoisted from a Maryland pond a few years ago.
Still, in aquatic environs, "Once an exotic species becomes established,
it's impossible to eliminate," Shafland said.
Shafland said he rarely nets any walking catfish while electrofishing - a
process that passes electric currents into water to stun fish for
population counts. He said they appear to be generally absent from open
waters and box-cut drainage canals.
Occasionally, people report catfish road crossings. A fish farmer from
Venus, Fla., said he once encountered this while driving in Boca Raton. At
first he thought the road ahead was moving, he wrote in an Internet
article, but "moments later I was driving over thousands of these fish.
The feeling was like driving over an oil slick."
Beyond suburbia, the walking catfish does dominate isolated pools of water
in marshes and culverts and certain types of ditches, scientists said. It
lives and reproduces in the Everglades.
Loftus, who has seen them wriggling across a road in Everglades National
Park, said large concentrations occur in some places, including the Big
Cypress National Preserve.
"Whether they are causing any ecological harm is a question that remains
to be answered," Loftus said. "Gauging by the low populations we see
normally, it's unlikely they're having much of an effect."
While not notably detrimental in nature, the walking catfish has meddled
seriously with the business that accidentally introduced it to wild
Florida: aquaculture.
The species has made raids on the ponds of fish farmers, where "they'll
eat all their crops," Shafland said.
Fish farm owners have responded by building levees and fences to keep them
out.
"The single biggest problem is with them crawling into aquaculture ponds,"
Shafland said.
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