Fishing Traps
A fish trap or "daouli" is a trap used for fishing.
There are not always baited to attract prey, and are periodically lifted out of the water.
A typical contemporary trap consists of a frame of thick steel wire in the shape of a heart, with fishing net stretched around it. The mesh wraps around the frame and then tapers into the inside of the trap. Fishes that swim inside through this opening cannot get out, as the fishing net opening bends back into its original narrowness.
Except fishes a lot of times we fish octapus, crabs and shrimps in the traps.