One of these came up behind us while camping in Cape Terriggan, I'm assuming it was fished up but it was strange because we were in the tunnel and it popped *behind* us fairly far from the nearest person fishing.
To make a long story short, it did NOT agro and we were definately levels that it would have agro'd if the level range on this page is correct, and we were definately moving around enough (I for one walked right around it before I knew it was there) for it to have agro'd by sound. But it definately did not.
I was fishing at the lake in Sea Serpent Grotto, when I herd the monster music, figuring I'd pull up a sea monk or a kraken I continued to catch the monster. Needless to say I was quite surprised to pull up a Stygian Pugil. So you can fish them in Sea Serpent Grotto as well.
I just scouted the area right near Cloister of Tides in Den of Rancor for xp. There are 10 of these guys right by zone, all checked it++ to RDM65 with sword@210 equipped. I heard a 65->67 party can take them, but hoping a static of 65s can...