Pair trawl

              Pair trawling means that the net is towed by two boats.  It both boats are small, less than 18 m long and with main engines of up to 150 h.p., it is a small pair trawl.  A medium pair trawl combines towing of a boat of over 18 m in length and with a main engine of more than 150 h.p., with a small fishing boat.  If both vessels are large, it is known as a large pair trawl.  This fishing method was introduced in Thailand in the 1960s by Japanese fishermen.

              In pair trawling, the net mouth is kept open by outward towing of the two boats, which always try to keep the same distance between them during operation.  Otter boards are not necessary, the arrangement of gear is simplified, the warp is connected directly to the sweep lines whose other and is joined to a triangular iron frame at the end of Gridles from each wing of the net.

              Setting: the cod-end is thrown into the sea, or pulled out by one boat, while the net boat keeps “dead-slow ahead”, lowers the net, and tows it until it is stretched.  The other boat approaches and the messenger line is thrown to it so as to transfer one wing of the net.  The sweep lines are then connected to the triangular iron frame on each boat, and both boats sail-ahead together, paying out the sweep lines and warps evenly to required lengths, and the fishing commences.

              Hauling: both vessels stop and turn toward the net position, warps are hauled and passed through gallows at the bow until triangular iron frame reach the gallows.  The boats then converge until they are a short but safe distance apart and sweep lines are disconnected, messenger line is thrown to the net boat in order to return the wing net.  Then net is hauled on board by manpower or by capstan winch passing through a pulley on the boom crane until the cod-end is hung and emptied.

              A pair trawl is usually operated in the day-time.  Fishing grounds are in the Gulf of Thailand and the Andaman Sea at the depth of water up to 40 meters.  Most catches consist of trash fish, squid, cuttlefish and threadfin bream.  The major landing ports are Samut Sakhon, Samut Songkhram, Songkhla, Ranong and Phuket.