You are assuming that access and usage rights arguments are based on the presence of fish and game. While anglers advocate for public waterway usage in order to pursue their sport, the access rights they argue for are not based on the presence of fish. The arguments is that waterways are public, therefore we should be able to fish them. The argument is not, "There are fish there, so the waterway should be public."
As it pertains to PA, navagibility applies to the most fowl AMD streams and best Class A waters alike. There are no stipulations regarding biological health or worth as fisheries.