Fisherman Scott Curry reeled in the 20-pound fish on Buffalo Springs Lake and immediately noticed the catch had human-like teeth. A game warden photographed the fish and is attempting to identify it. General Manager of Buffalo Springs Lake Greg Thornton told KLBK13-TV in Texas that he has never seen anything like the fish in the 36 years he has lived near the lake.
The leading theory is that the fish is a Pacu, about which Wikipedia has this entry:
The Pacu is a common name used to refer to several species of South American freshwater fish that are closely related to the Piranha. They are vegetarian or omnivorous and are commonly kept as aquarium pets. They have unusual teeth, which strangely resemble human teeth, which they use to crush seeds that fall into the water. Pacus have been illegally introduced as exotic species throughout the world into freshwater habitats, including discoveries in the United States in Utah, Colorado, Minnesota, Michigan, Arizona and Texas.
I'm hoping that Big Gary (as the MoH's fish expert) may be able to shed some light on this.