Try Darby Ck. It would not surprise me if they are already there or that they soon will be. They have been at the base of Fairmount Dam on the Schuylkill so finding them in Darby wouldn’t be a stretch. Likewise, it would not surprise me if they could be found at the base of Hulmville Dam on the Neshaminy, Bucks Co. Even the tidal portions and a few hundred yards above the tidal influence in DelCo streams may have some promise, as other river species such as adult channel cats, small stripers, and occasionally American shad fingerlings utilize some of the tribs during the official summer months.