somebody just cought a seven and a half pound piranaha from the james river here in virginia.it was cought near a hot water distarge from a power plant.
it could be a piranha that somebody released when it was smaller. If there is a hot water discharge from a power plant it could probably overwinter without a problem.
The only Ps that could get that large would be a rhom, manny, or piraya and I think anyone with those rarer/harder to get species would have known at least a little bit about P's and their value not to release them. Therefor, I will bet my left testicle that it was a Pacu!