A pacu carcass, in the submitted photo at right, was found on the bank of Glade Run Lake in mid-December. Pacus are a species of South American freshwater fish related to piranhas. Members of Glade Run Lake Conservancy believe the fish must have ended up in Glade Run Lake after someone tried releasing it into the wild.

MIDDLESEX TWP — While walking Dec. 10, Jefferson Township resident Tom Cook saw something new on the bank of Glade Run Lake.

The foot-long carcass of a pacu, a South American freshwater fish related to the piranha, might have gone unnoticed if Cook's buddy's dog hadn't rolled in it.

Cook said he immediately knew the fish probably didn't belong in the lake, which was drained in 2011 and restored in 2017.

“I noticed the teeth,” Cook said.

Like piranhas, pacus have distinct teeth. Unlike piranhas, a pacu's teeth are human-like. This helps with their omnivorous diet, which includes nuts.

Cook took pictures of the carcass to show to members of Glade Run Lake Conservancy. The conservancy believes the pacu must have been released into the lake by someone who had it as a pet.

“The way I understand, it was very close to the water,” said Dave Fowler, a board member and founder of the conservancy. “That's a big problem.”What's worrisome is not that the lake might now be infested.Freeman Johns, a fisheries biologist with the Pennsylvania Fish & Boat Commission, said outdoor water temperatures in Western Pennsylvania are too cold for pacus to survive.Still, Johns said that doesn't mean it's OK to release them in the wild. Introducing any plants or animals from outside sources into the lake can introduce invasive species and diseases.“It does happen,” Johns said. “We really discourage people from stocking fish.”Johns said even moving native species from the Allegheny River or Lake Erie into Glade Run Lake can be damaging.Fowler said it's the first time Glade Run Lake has washed up a pacu. There have been instances of other creatures being dropped off, such as domestic ducks.

In the case of the fish, Fowler said the conservancy immediately got in touch with the fish and boat commission.The conservancy knows how things like a pacu drop-off can upset the trout fishery being established at the lake.The fish and boat commission has been stocking catchable trout, according to Johns. Fowler said large mouth bass that were “fingerlings” three years ago are now 10 to 12 inches.“It's a delicate balance,” Fowler said. “The habitat potential for this lake is really, really good.”In a Jan. 2 blog post on the conservancy website, Fowler asks lake visitors to be considerate.People who wish to get rid of non-native animals should consult an appropriate pet shop, zoo or aquarium, veterinarian or similar professional.Trying to release creatures into the wild can pose many problems — for both people and wildlife.“Let the professionals do their job,” Fowler said.Johns said the fish and boat commission has a very simple rule it asks citizens to follow.“Don't move fish around,” Johns said.

A dead pacu found on the bank of Glade Run Lake in December shouldn't have been able to survive very long in the water, according to the Pennsylvania Fish & Boat Commission. Pacus are South American freshwater fish similar to piranhas, and can't live long in cold temperatures.