Where you will find wild trout on the Manatawny in other than very low (if any present at all) densities is highly dependent upon location. Because of summer water temps, the stretches with higher densities of wild trout that are worth fishing over are much less common than the stretches with low densities of wild trout, even in Pa's coolest summers. If you know where those good stretches are I am sure that fishing can be fun throughout most of the year.
correct me if im wrong but people think there no fish because its not an easy stream to fish you need to think and keep you eyes open lots of little pockets im glad its finally getting cooler.
In general, given the length of the stream, you would need to cover a lot of water to find the fish; but if you are fishing the few locations of which I spoke, you would not have to cover much water at all. The wild brown populations are pretty good in those 300 yard long to 3/4 mile long stretches.
I should add to my comment above (#9) that given the geology of the area, it would not surprise me if there are other isolated, short, colder stretches that individuals have found where wild brown trout densities are similarly higher.