If you asked a few crabbers what is the best bait to use for crabbing and you will probably get as many different answers. And each would have his success story to back up his bait preference.
 
From observation, most commonly used baits like fish carcass, chicken carcass, lamb necks, lamb shanks, beef off-cuts, beef bones and canned cat food do give results although it is difficult to pin point the best performer as too many variables are at play when a pot is deployed in the water.

 There are others who swore by squid, prawns or molluscs (clams) as the premium bait to use for crabbing but besides the high cost to procure them or more efforts to gather them from the wild, the expected higher return of investment is not guaranteed nor proven.
 
Since the common baits are inexpensive and easily available, it therefore make a lot of sense to use these in exchange for the more valuable and tasty crabs then to trade them with premium seafood like prawns or squid.

Also, the bones or skin found on these commonly available baits provide a tough structure to secure them firmly to the pots. The exception is the canned cat food where about half a dozen holes are punched on the can and threading a steel wire through two of the holes to secure it to a pot.

The use of canned cat food made of tuna is the only processed bait and it is getting more popular amongst recreational crabbers. It has the advantage of a long shelf life as it is non-perishable unless opened and lower grade products are relatively cheap and readily available from any supermarket. They can be bought in bulk during offer sales and kept in the pantry for long period of time.

Crabs are attracted into a pot by the smell of the bait that disperses through the water and it has been suggested that crabs are attracted to a can of cat food more by the tuna oil than to the processed tuna meat. As such, baits like fish, chicken, lamb or beef become less effective after some time in the water as the smell gets washed away. In order for the stale baits to be effective, fresh bait must be added to the pot at least once during the middle of the crabbing session. Alternatively, lightly coating the stale bait with a layer of tuna oil may work as well. These tuna oils are used by fishermen as berley and are commonly available from tackle shops.