The bizarre animal was discovered in a lake in Delran, New Jersey, by Ron Rossi and his son Frank, who were fishing at the time.
Initially the duo thought the fish was a carnivorous piranha before realising it was a harmless species called pacu.
The fisherman confessed they were shocked to find the pacu - which are cousins of the Piranha and have human-like teeth - in the lake as they usually can't survive in cold water.
A spokesperson from the Department of Environmental Protection told Action News: ''Many times, these fish are deposited into lakes by pet owners.
''These fish do not survive in colder water, so we encourage people not to release it into the wild.''