Were bluegill introduced or did they just migrate? Were small ones or eggs dropped out of the sky by birds or weather events? I severely doubt they were introduced to certain watersheds by man but I am not entirely sure.
If you're trying to make the argument stating bluegill and brown trout are both invasive species I don't think you really have ground to stand on. Bluegill primarily live in ponds so they're isolated and their effects are on that exact body of water. Yes, I know they live in moving water too but they have a preference for stillwater. I have NEVER seen any documentation about bluegill having a negative impact on a certain watershed but I am also not part of the fish biologist scientific community so if someone cares to provide evidence suggesting the harmful effects bluegill have on a certain watershed and their evidence is sound I will take that as bluegill being a harmful invasive species.
Brown trout on the other hand have been proven to be harmful. Forget how high they are on the list but I think it's around 30 in a list consisting of 4000 species. This is a list I got from
@Fish Sticks. That's a pretty high rating in terms of how dangerous they are. Bluegill also don't have organizations defending them and their harmful effects. Bluegill don't have people refuting scientific data about their harmful effects. I also don't think bluegill are stocked in PA and certainly not stocked in watersheds where they are displacing and ultimately eradicating other species merely by existing. I know that they take over ponds but I don't think they have been introduced by man. There isn't a multi-million dollar agency farming bluegill for the express purpose of getting more license sales and introducing bluegill into unwanted watersheds.
Ultimately bluegill aren't trout, so they don't get the same rights as trout do, so f*** em' I guess. Humans are quite good at playing god and assigning value to certain species aren't we?