I have seen them in Lake Erie, some pretty good sized ones, a few pounds. We have seen them there since we were kids, just guessing escapees from flooded ponds, or people releasing them when they tired of them.
Most if not all are a member of the carp family? My brother has used them for bait in Lake Erie, small ones, they work, pretty hard for them to blend in with their surroundings. Never saw a small one in Lake Erie, I think they get found and eaten pretty quickly. In a shallow whats his name without predators?