Well, Dave... I probably could have put it a little better and certainly, I'm working from dated information and largely from memory. Let me try and explain myself this way:
There is (or was at any rate) a distinct difference in the trout carrying abilities of the streams in the lower Tionesta basin (let's say from Lynch downstream) and the vast majority of the Clarion basin when contrasted with the streams in the Upper Tionesta basin and (many of) those in the Kinzua basin or direct tribs to the River.
In the early 90's for example, if I recall correctly, the combined Clarion basin and lower Tionesta drainage had 4 class B stocked stream sections, Hoffman Run (2), Ross Run and one section of the EB of Spring Creek. By contrast, the following streams in the upper Tionesta and direct Allegheny or Kinzua drainages were Class B or had Class B sections, 15 stream sections in all: Sugar Run (2 sections), NB Sugar Run, one section of the Chappel Fork, Two Mile Run (2), SF Kinzua Creek, Four Mile Run, Six Mile Run, NF Six Mile run, Browns Run, Little Hickory Creek, West Hickory Creek, Wolf Run (SB Tionesta watershed), Hemlock Run (at Kinzua dam). What is inportant is that in these stocked streams, the Class B biomass being measured was primarily brown trout.
Additionally, among wild trout pops in unstocked streams, many many more in the combined Upper Tionesta/Direct Allegheny drainage had mixed BT/ST pops or in some cases, dominant BT pops than in the Clarion/Lower Tionesta draiange where when wild trout were preseent , they were almost always the more acid resistant brook trout. While dated, this information comes from the AFM files at Tionesta.
So, I think I'll largely stick by what I said. The more severe acid depression of cold water fisheries in the ANF region is (or was) far from uniform or area wide. It was much worse in the lower Tionesta and Clairion drainages.
So far as the comparison with NC PA drainages like Pine and Kettle, this isn't my idea. It came from a Commission biologist who said that in many ways the better streams in the ANF were not at all chemically dissimilar from streams of the NC mountains. He didn't have an answer when I asked him why the fiseries are often so starkly different, but he suggested episodic extraction activity and the attendant sedimentation was a likely factor.
I'm just the messenger....