Not to be that guy, but lobsterman is 1x1, and takes damage like one.
As about dealing with them, he's suspectible to any choking damage, so yes, if you're bold enough, you can knock him out with rope. Cutting damage works well, too, but it's not limited to melee weapons - throwing axes in proper hands (and in proper amount) will cut them apart, as well as well-placed burst from arena flak cannon.
He also takes 100% damage from bio and mind; that makes poisoned daggers\blowpipes\cobra staves an obvious choice.