3. Bottom Otter Board Trawl with Booms
Presently, in most provinces throughout the country there are many fishing boats catching shrimp, fish and other marine resources using the bottom otter board trawl with booms. To increase the horizontal opening of the trawl mouth, two booms are used on each side of' the boat. Thus, the fishing efficiency of the gear is increased.
The bottom otter board trawl with booms for catching shrimp is not very different in comparison to an ordinary otter board trawl. The mesh size of the net for catching shrimp is 35 - 50 mm in the wings and the mesh size of the cod-end is 20 - 25 mm. But to catch demersal fish and other species, the mesh size is bigger, with the mesh size of the wings ranging 80-240 mm with 30-40 mm at the cod-end.
The boom is used to increase the horizontal spreading of the otter boards because of the increased distance between the two towing warps.
The operation of an otter board trawl with booms is the same as for an ordinary otter board trawl. The setting of the towing warps reaches to the necessary length and links to the messenger ropes at the two ends of the booms.
The trawl winch hauls the messenger ropes. Following that, the board is hung on the gallows, and the net is collected by the common method of using an auxiliary vessel. The end of the sweep line is linked to the headline leg and tow leg of the wings. This requires the two vessels to work in synchronization to set the sweep lines, then the towing warp. The length of the towing warp depends on the fishing ground.