Crab traps are very similar to lobster traps but are square shaped instead of rectangular. They also have the openings on the top of the trap and do not have knitted heads like a lobster trap.
Many Gloucester fishermen have fished out of Naples at one time or another, mostly longlining for swordfish back in the day. Mark Ring has a few great stories he tells from his days fishing in this port, none of which I can repeat here.