Tilapia discovery shows invasive fish problems

By Deborah Weisberg Contributing Writer

Pittsburgh — The rivers here may be a dumping grounds when home
aquarists clean their tanks, but tilapia in the Monongahela River
this summer were a fish of a different color.

Raised as table fare in farms across America, including
Pennsylvania, and sold live in markets, such as Wholey’s in
Pittsburgh’s Strip District, tilapia can be a real nuisance even in
the northeast.

“They breed like gangbusters – often and prolifically – and they
grow quickly,” said commission biologist Rick Lorson. “They’re an
invasive problem down South and the last thing we want in our
waterways.”

Lorson’s staff documented the presence of tilapia near Braddock,
but failed to net them during electro-fishing a week later.
“Conditions were poor or they may have moved downstream,” said
Lorson. “At this point, we’re going to wait and see what
happens.”

Almost 20 years ago, tilapia caused a mild panic on the
Susquehanna River when escapees from a fish farm at Brunner Island
near Harrisburg found refuge in the warmwater discharge of a power
plant. “We took unprecedented steps to get rid of them,” recalled
Bob Lorantas, the Pennsylvania Fish & Boat Commission’s chief
warmwater biologist. “We got the discharge temporarily shut off
until they died.”

Pittsburgh Zoo and Aquarium biologists also identified the Mon
River tilapia after they were contacted by John Pinigis of
Swisshelm Park who had been watching and catching them for two
weeks near Braddock. “There are usually at least 10 of them, all
schooled up and then pairing off,” said Pinigis, who landed them on
redworms and chunks of algae he scraped from rocks. “Most of them
were beige-colored but some were dark, and they were thin and round
like white bass. They have a different kind of mouth.”

Tilapia are omnivorous, with forward feeding mouths that let
them forage throughout the water column. “The zoo people told me
they would be eating hippopotamus dung back in Africa,” said
Pinigis, who kept three, up to 12 inches, for his backyard pond,
but gave two to Lorson for research. “That might be why they’re
hanging around the sewage outflow.”

How they wound up in the Mon is anyone’s guess. Since the
Susquehanna River incident, Pennsylvania permits tilapia farming
only in enclosed facilities, such as the one near Harrisburg that
supplies Wholey’s in Pittsburgh with live tilapia for a niche
clientele. “We sell about 1000 pounds of live tilapia a week,” said
company president Jim Wholey, who has the fish swimming in a big
tank.

“We started the tank just for show but it’s become really big.
We have an Asian trade whose cultural practice is, for every fish
you eat, you release one. They go home with two bags – dressed fish
in one and live fish in the other.”

Evidence of ritual releases of fish – a practice University of
Pittsburgh Chinese culture professor Xin Min Liu says has ancient
Daoist origins – is largely anecdotal, perhaps part urban legend.
But growing immigrant populations in many major cities have driven
up the demand for live tilapia and other exotics being supplied by
farms all over the country, where even species such as big head
carp have replaced traditional, soil-based crops.

The American Tilapia Association says its growers produce 20
million pounds of live tilapia a year for a primarily U.S. Asian
market, because those consumers prefer eating fish soon after they
are killed. Experts say evolving ethnic communities and a switch
from agri- to aqua-culture are posing new threats to natural
resources.

”It’s a thorny problem since aquaculture facilities are on
low-lying rivers prone to flooding and can’t be completely
bio-secure,” said Phil Moy, an invasive species expert with the
University of Wisconsin. “And you’ve got these cross-cultural
hurdles to overcome, where some people like their food to be
wiggling when they buy it so they can release it for good
luck.”

”There needs to be a reckoning between the big business of fish
farms and conservation.”

As a case in point, he said, snakeheads raised in a Crofton,
Md., pond by an Asian grocer got loose a few years ago and now are
breeding in the Potomac River. Around the same time, big head and
silver carp escaped from a flooded fish farm on the Mississippi and
now live in the Illinois River. A $9 million electric gate is being
built to try to keep them out of the Great Lakes.

”It’s probably only a matter of time before all of those species
make it to Pennsylvania,” said Fish & Boat Commission spokesman
Dan Tredinnick. “They’re the nastiest exotics and they’re banned
here. Snake-heads and big head carp are a bigger threat than
tilapia, although that’s an exotic we don’t want in the wild
either.”

Ironically, some of Pennsyl-vania’s most coveted gamefish,
including brown and rainbow trout, were considered exotics before
the term was ever coined. They were imported from Europe more than
a century ago. So, too, was common carp, although it fizzled as a
food fish and has gained only grudging acceptance by all but a
small following of specialty anglers.

Its cousin, the grass carp, is an unwanted exotic, which parts
of Canada on the Great Lakes are trying to ban for sale as a live
food fish.

A Pennsylvania man killed a 54-pound grass carp with a bow and
arrow in Erie’s Presque Isle Bay this spring and tried to claim a
state record, although its size, while bigger than any common carp
ever caught here, is small by grass carp standards.

Today, it is illegal to plant any non-native fish in
commonwealth waters because they could introduce disease,
out-compete established species for food, and upset the existing
biodiversity. Until recently, unauthorized plantings have usually
been pacu dumped by a home aquarist and doomed to die by summer’s
end. But the threat of invasives has environmentalists and
regulatory agencies scrambling to address a whole new set of
concerns.

The Massachusetts Institute of Technology’s SeaGrant program has
produced a brochure “Into The Pan Not Into the Wild” in five
languages, including Chinese and Korean, to discourage the
ceremonial release of exotic food fish.

“We know the practice goes on, but getting anyone to admit it is
difficult,” said marine biologist Judith Pederson, a Johnstown,
Pa., native who now lives in Wooster, Mass., and runs the
program.

“There are language and cultural barriers and a wariness in the
Asian community about people from the outside telling them that
what they’re doing is wrong.”

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