The a-pacu-lypse is upon us. As if US waterways weren’t teeming with enough invasive fish of late, a Texas angler caught a South American piranha relative with “human teeth” at a local lake on Sunday.

Piranhas belong to a family of bony fish characterized by highly developed dentition. They’re cousins to the pacu fish, which has dentition eerily similar to human teeth. Unlike pacu teeth, which are ...