Just in general in Nova Scotia you don't need any license for non-commercial fishing in tidal areas (still need to observe bag limits though.) You do need a license for any fishing in fresh waters.
If you're hand picking crabs you're fine. Just don't set any traps or snares, but you might want to check to see if they are safe to eat. Sometimes the close areas for shellfish harvesting due to food safety concerns.
The murder that dhughes is referencing had more to do with it then them just catching someone cutting their lines, there was a long history between the victim and the boat crew.
