You can find it at a water area (I found it at the edge of the map). To knock him out, for starters, use a slingshot. When he is down bring your narcotics and berries. If he is unconscious and you fear he will wake up, punch him a few times to keep him like that. Congrats, you now have tamed a Carbonemys. Hope this helped.
Side note: if you want to be safe, through a bola and hit him with a bat to knock him out.