I've fished the Lehigh Valley limestoners since the 70's and grew up about 1/2 mile from the mouth of the Bushkill, albeit on the NJ side so I am a foreigner. IMHO, all peaked about the early 2000's and have seen a decline. Of course the Saucon was dead in the 70's and has had a more recent rise and decline
It went in phases. All had lush weedbeds in the 70's. One could run their hands through the weeds and come up with a handful of scuds and cressbugs back in the day. The fish put on weight all winter in this environment. This was before scud hooks and I remember a buddy getting a hold of curved English bait hooks on which we tied simple hare's ear or muskrat dubbed bodies and slayed bigger browns, especially at the old special regs area near Tatamy. Then by the 90's the weedbeds seriously declined and now they are hard to find. The flood/drought yo-yo starting with Hurricane Floyd in 1996 then seemed to add sediment in most places and strip the gravel down to bedrock in other places. It seems like the stream beds are increasingly broadening and composed of sand. A similar thing happened to my local stream, the Upper South Branch of the Raritan. The section still holds a better than expected brown and a variable brookie population. However, the slimy sculpin population has crashed, which concerns the local biologists, but few anglers.
The Heritage Stretch IMHO also suffers from poor stream "improvement" design with the old downstream vee gabions. These eventually cause the stream to widen and add a lot of sediment. Newer techniques mimicking the point bar/ riffle/hole structure of natural streams seem to hold up better IMHO.
