If you have room, take a 2 litre soda bottle, cut the top off and insert it backwrds, into the base section. Shazam, you have a trap. Place a piece of raw shrimp in there and wait. Be sure the opening is large enough for him to pass through. Once in, he will not be able to exit.
Good Luck!
BTW, the cut location is at the largest radius under the top opening