No. 9: Testicle-Eating Fish Spotted in Illinois Nothing got guys crossing their legs, cupping their crotches and wincing like this story. The pacu -- a toothy fish that can weigh up to 55 pounds -- was spotted in Lake Lou Yaeger in Illinois in June. Pacus are native to the Amazon Basin. They generally eat nuts, snails and aquatic vegetation. But when they come into human contact, they've been known to bite off the testicles of fishermen and swimmers.