Yellow perch are a coolwater fish and I've not had any problems with temps in the upper 80's with smaller fish. However once they get larger than 12 inches they go off feed in warm temps.

So yes it's the warm end of the temp spectrum they have trouble with.

They also need an extended period of coldwater to develop normal eggs.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.