Dan.
The “wild” brook trout in Wyomissing Ck in Mohnton threw us for a loop as well, so much so that we electrofished every near-by trib of any size to try to locate the source of the fingerlings. We only found wild browns in the tribs and the rest of the main stem of the Wyomissing. We then completed our digging into the possibilities, particularly since we only found the brookies at one site on the Wyomissing and at an odd location...in town instead of the headwaters.
I eventually tracked down the source, which was the “Trout in the Classroom” program. The kids had raised brook trout to fingerling size and then released them within 100 m of where we collected about a half dozen of them two or three months later. They looked exactly like wild fish...no fin damage and great colors. Frankly, I never thought that we would find multiple fish from that program a few months later in any stream except for perhaps a limestone spring without competitors.
As a side note, Wyomissing is now a Class A stream from the old Mohnton Dam site (now breached/removed through PFBC initiative, habitat restored) at the upstream end of town to the headwaters in addition to the original Class A limestoner stretch in the Wyomissing Boro Park downstream to Museum Rd in West Reading. I don’t know if you were still in the area when agencies were able to successfully press for the Museum Dam to be breached. That formerly impounded stretch immediately went to Class A. In the past few decades the stream went from no wild trout below Museum Rd to the Schuylkill R, then went to Class C or B about 10 yrs ago, and most recently supported few or no wild trout again. Will PM my email address.
Mike