Learning whether the species is harmful to native or migratory fish in the region could also reveal its potential impact on the recreational fishing industry. The flathead is native to southern and western waters, and in Pennsylvania occurs naturally in the Great Lakes and Ohio River drainages. Anglers have been introducing the species into rivers of the eastern two-thirds of the state, and the species spreads quickly through its new home, where it becomes the top-tier predator. The flathead grows to more than a hundred pounds in some southern and western waters, but 20-30 pounds is more common in Pennsylvania.