Pretty off the wall post you responded too considering Goldfish/Koi are domesticated and Man Made. The only living species in that hybrid is the Prussian Carp also not native too the Americas. Siberia is it's origin but it has infiltrated most of Europe and Asia. There are no indiginous species of carp in the Americas, ones they think might be are heavily debated. The Carp in the Americas were imported and fish farmed and stocked to bolster our waterways and ponds with more live stock. In some cases like the Silver Carp which were used for algae control have become invasive.
Carp are cold water fish, odds are most wild Piranha have never seen a Carp.