Why these morons can't figure out how these fish got upriver is beyond my comprehension. The Delaware and Chesapeake Bay are connected by a canal and water flows in both directions depending on the tide. They have been lifting and transporting shad for years around Conowingo. It's not too hard to get a couple of other fish into the mix.
Anybody eat fish out of the Conowingo? Isn't that the cooling pool for Peachbottom Nuclear?
My family was wading in the shallows of the Susquehanna below Safe Harbor Dam back around 1983, when my kid brother steped in a shallow pool and was startled out of his wits by a 3 ft. long catfish. Never saw the boy jump so high in my life as when he stepped on that thing!
Plus catfish are son-a-bitches they live forever plus they can skip along dry land for quite a long distance without taking air like other fishes. Same with eel's.
My guess would be that they swam there?