Dundalk fish tale loses its bite

Experts conclude catch in local pond is pacu, not piranha

September 30, 2006|By Candus Thomson | Candus Thomson,Sun reporter

Call it a red herring. Or a pacu-lips now.

Either way, it appears the fish caught at a Dundalk park pond last Sunday was a pacu, not a piranha.

Both fish swim in the same fish family and are often mistaken for each other. Earlier this week, two biologists were fooled, as were several veteran fishermen.

"I can understand the misidentification," said Tom Lorenz, an invasive species researcher at the University of New Orleans. "The red is similar on the body. A lot of people buy [pacu] thinking they've purchased piranha, and when they get too large, they throw them in local waters."

The big difference between the two fish is that the piranha might feel at home chowing down at an Outback Steakhouse while the pacu would be happier grazing at a salad bar. Neither would survive Maryland's winters.

People who keep piranha in home aquariums are sensitive to cases of mistaken identity. Many warm-water states have banned them, fearing a population could take hold and upset the local ecosystem. In e-mails to The Sun, many fish-store and aquarium owners expressed concern that Tuesday's story about the Dundalk fish could prompt Maryland wildlife managers to roll out the unwelcome mat.

Dr. William L. Fink, director and curator of fishes at the University of Michigan Museum of Zoology, said he has no doubt that the Dundalk fish is a pacu. He offered one identification method: "If there are two teeth behind the front-row teeth, it's a pacu. If there is only a single row of teeth, it's a piranha."

One of the world's foremost authorities on piranha and pacu, Dr. Ning Labbish Chao, concurred with Fink's identification. The former research associate at the Smithsonian Institution who is based in Brazil and works for Baltimore's Bio-Amazonia Conservation International, gave this tongue-in-cheek field identification method: "Stick your finger in the mouth. If it cuts and blood gushes out, that is piranha. If it hurts with marks and blood seeping out, that is pacu."

The fish biologist who examined the Dundalk fish and made the initial identification has worked for the Maryland Department of Natural Resources for 20 years and at Baltimore's National Aquarium before that. Marty Gary said that while he was sure of his identification at that time, he would defer to the experts.

"The dentation didn't look like any pacu I had seen," Gary said. "A piranha, normally the teeth are tri-cuspid. When I pulled the jaw down and looked at those things they clearly looked triangular and not like any pacu I had ever seen."

In the past several years, DNR has collected pacu from Bynum Run Park near Bel Air, the Susquehanna River near Peach Bottom and near Port Deposit, a pond in Bowie, a golf course in Calvert County and a Potomac River tributary.

But on one issue, everyone agrees: Whether the exotic fish is a pacu or a piranha, whoever dumped it has the brain of a minnow.

"I think the take-away message from this is the same either way," Gary said. "No. 1, don't release exotics into Maryland waters, and No. 2, when you make a commitment to have a pet, know what you're in for and be prepared to deal with it responsibly." candy.thomson@baltsun.com

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