The toothy, nearly 3-pound fish Norwich angler Jeff Breault snagged Monday evening is not the much-feared, sharp-toothed piranha.

Anglers, it is safe to go back to the Shetucket River.

The toothy, nearly 3-pound fish Norwich angler Jeff Breault snagged Monday evening is not the much-feared, sharp-toothed piranha.

It’s a pacu. Despite being a freshwater native of South America, the fish aren’t complete strangers in Connecticut’s waters thanks to desperate pet owners illegally dumping a particularly fast-growing member of their fish tank.

“They’re attached to the animal and they don’t want to kill it,” Neal Hagstrom, a senior fisheries biologist with the Department of Environmental Protection, said.

A 2-inch pacu can grow to about a foot long in a year, according to Gus Stout, a senior aquarist at Mystic Aquarium, and up to 3 feet at maturity. In the wild, Stout said the fish swims through the forest floor during the Amazon River’s seasonal floods and grinds fruits, nuts and vegetables with its flat teeth. In Connecticut, Hagstrom said it snacks on water plants and the occasional worm on a fisherman’s hook.

Or, in Breault’s case, an oatmeal ball originally meant for a carp. The 20-year fishing veteran landed the fish at the bottom of Roth Street. “It was fast, but it wasn’t strong,” he said.

The fish lived for a few hours in river water in a five-gallon pail, Breault said, but it did not survive the transfer to a buddy’s tank. Both Hag-strom and Stout agreed the warm-water fish would have died in Connecticut’s chilly winter waters. Still, Breault said the pacu is a keeper.

“That’s too bad that somebody would let it go like that,” he said. “I’m going to get it mounted anyway.”

Reach Erica Jacobson of The Norwich (Conn.) Bulletin at 860-425-4241 or ejacobs@norwichbulletin.com.