I have not seen a brook trout in the Letort since before the 1982 fish kill (some kind of spill at the cress farm). That was a decent fish (for a brookie) maybe 13 inches. Hit a black marabou streamer with a red throat. I had too much line out and missed him. I'm fairly sure it was a stocked fish.
In those days, a fair number of stocked brookies and rainbows would swim up out of the kids section in Letort Park below the Fox spawning grounds. When I say a fair number, I'm talking about seeing one or two fish a season, so more curiosities than anything else. I haven't seen anything but browns in the creek in a very long time, but there were many years when I was raising kids when I didn't fish creeks where there was a good chance of not catching anything. I enjoy fishing when I don't catch fish, but I enjoy it more when I do. Plus the Letort is kind of a chess game you need to plan out and make sure you've got your moves prepared.
Anyway, the Letort is real brown trout water, a classic English or Croation chalk stream. Certainly before 1883 it was brook trout only, but a 12-inch brown would have no trouble eating a dozen sexually mature brook trout in a season (and becoming an even bigger and more ravenous fish that eats even more brook trout). If the wild brook trout in Big Spring are any indication of what was in the Letort pre-1883, it's hard to imagine any substantial wild brook trout population in living memory because most of them are the perfect size for brown trout meals.
Add in that the cress farm was hardly the kind of pristine environment brook trout seem to need, I am doubtful about the prospects for a remnant heritage strain of brook trout having held firm in that little section of creek just above the main cress farm.
That said, it's probably worth looking into the state of the fish population in the left branch. If there is a heritage strain of brook trout up there, it would be something of a genetic gold mine.
As for that chalky cast, I always presumed that it was related to the activities at the stone crusher, either dust getting into the creek from the crushing operation (it sure coats the leaves of every plant down there in the spring and summer), or something related to water being pumped from the quarry, or some combination of the two.
I came to believe it was cress farm related only after the cress farm shut down and the water downstream became reliably clear, even when the roar of the stone crusher was blasting my ears.
Like I say, the Letort is endlessly fascinating, and that clear water down all the way to the Conodoguinet make me optimistic it could be the scene of a renaissance possibly on a scale even bigger than what Norm Shires and his colleagues were able to accomplish on Big Spring.
With the future holding such bright possibilities, the good old days ain't what they used to be.