From what I just read, these are actually Flathead cats and they are apparently one of the "tastiest" invasive species in MD just like the snakehead.
From the Maryland DNR.
"Flathead Catfish have taken up residence in the lower Susquehanna River and particularly at the Conowingo Dam pool. They are considered an invasive species in Maryland but like the notorious snakehead, are one of the tastiest invasive species youd ever want to meet."
Doesnt look like the flathead all that much to me though...