Modified Lobster Traps for Catching Crabs and Keeping Lobsters Out

Before redesigning lobster traps for capturing crabs and excluding lobsters, laboratory tests were done to determine the ability of both crabs Cancer irroratus and lobsters Homarus americanus to pass through simulated trap entrances and escape holes of various sizes and shapes. A long rectangular opening 44.5 mm (1.75 inches) wide allowed most crabs to enter, yet prevented passage of most legal-size lobsters. For use as escape holes in traps, round openings were found to be more effective than square ones to allow escape of lobsters while retaining commercial-size crabs.Lobster traps were then modified by closing the fishing heads and providing a long rectangular entrance at the top of the trap. Trap entrance widths of 44.5 and 51 mm (1.75 and 2.0 inches) fished crabs equally well; traps with a 38-mm (1.5-inch) entrance, and unmodified lobster traps caught fewer crabs. No lobsters were caught in the modified traps with entrance at the top.