I've taken to carrying a stream thermometer with me over the past year and have only seen stockers behave like that and only when the water gets warm (above 65). The fact that he's hanging out in the open like that must mean that there are very few places that have an acceptable combination of slow current and acceptable DO......at least thats what I gather. Look how hard he is puffing. Although I see plenty of fish in those conditions, they are never in the mood to feed, and I prefer not to fish those conditions. Perhaps the strange behavior indicates brain damage. Premorbid. If you did catch him, I'd keep him. With it being early July, chances are about zero he will survice through the summer.
Very nice video, that fish is a pig.