Surrounding nets with a purse line (purse seines)

              According to fisheries statistical record for 1982, there were 840 registered purse seiners.  Most of them were in the 10-100 gross ton category, and used luring devices.  Some had modern equipment on board, such as wireless set radio communication, echo-sounder, sonar, and radar. In 1985, some boats even had satellite navigation.  Many auxiliary fishing gears were used on board; capstan winch (mechanical of hydraulic), davit pulley, boom crane, electric generator, fish luring lamps and power block.  There were no freezers on board; instead, wet or dry ice was used.  A characteristic of this method of fishing is a rather large manpower requirement, which may, in time, become a disadvantage.

              Chinese or two-boat purse seine (Uan tang-ke)

              This kind of purse seine has been known to Thai fishermen for nearly 60 years.  It has not changed much during that time, except that cotton netting has been replaced by nylon, and fishermen on longer sail around looking for fish but rather use fish luring lamps.  This old-fashioned gear still remains in use on the Andaman Sea coast (Phuket, Trung, Satun), because of its special advantages, such as low operating cost, effectiveness in difficult fishing grounds and good commercial value of catch.

              Several vessels are required for an operation.  The mother boat is a 16-20 m long wooden vessel with a 100-250 h.p. main engine.  To rowing-boats (8 x 2x 0.8 m) are used as net boats, and another rowing-participate in an operation.

              The net is rectangular, 350 x 60 m, made of black-colour 25 mm nylon 210 d/9-12. Polyethylene, 25 mm, 380 d/15, is used for selvedge.  Two purse lines, polyethylene cross-rope, 28-32 mm, are fixed to the middle of the net.  The net is spread out by two rowing-boats, in areas around islands or banks, where the bottom is rocky or sandy hills.  The catch includes scad, barracude, cavalla, trevally Spanish makerel, mackerel and bonito.

              Anchovy purse seine (Uan lom chub pla katak)

              This gear is similar to anchovy surrounding net, except that a purse ring is attached to the sinker line, and the bottom of the net can be closed with the purse line.  A 10-20 m wooden vessel with a 20-150 h.p. engine, and 10-30 fishermen are needed for fishing operation.
              The net is rectangular, 250-400 meters long and 15-50 meters deep. Float line is shorter than sinker line (E=0.83/E=0.93).  Main net is blue polyethylene minnow net 2 x 2 mm and/or green nylon rachel net 6.5 – 8.3 mm 110 d – 210 d/5.  Polyethylene 380 d/12-15, 25 mm, is used for selvedge at sinker line.  Iron purse rings are attached on sinker line at intervals of 1.5-2 meters.  A 26-32 mm polyethylene cross-rope is used for purse line.  Buoyancy force is about twice the sinking power.

              A fishing operation is usually conducted in the early morning and evening time.  Fish schools are saught by eye, but sometimes fish luring lights are operate at night.  Anchovy purse seine can be found on the east coast of the Gulf of Thailand (Rayong, Chantaburi, and Trat), the southern east coast (Surat Thani) and the southern part of the west coast of Thailand, in Phuket, Krabi and Satun.

              Thai purse seine (Uan daum)

              Before 1960, most purse seines in Thailand were of this type.  The difference between this and any other purse seine lies not so much in construction, but in the manner of operation.  Nowadays, large vessels have sonar equipment for fish detection, but in the past and even today in the case of small vessels, a fish school has to be spotted by eye, in the twilight.  Sometimes, however, Thai purse seines are operated with the fish luring lights and fish shelters, which causes some confusion in fishery statistical records (see Table 1.4).

              The fishing vessel is 14-14 m long, with a 20-200 h.p. engine, and 10-30 fishermen on board.

              The net is rectangular, 400-600 m long, 70-110 m deep, cod-end is in the middle of the net.  The main net is 25-43.8 mm nylon 210 d/6-12, float line is shorter than sinker line (E = 0.6-0.7/E=9.65-0.75).  The buoyancy force is 1.3-2 times higher than the sinking power.  The colour of the net is black or green.

              Fishing operation is conducted from a single boat.  The net is hauled by hand on both sides of the boat, whereas the purse line is pulled by a capstan winch which is driven by the main engine.  The catch consists largely of Indo-Pacific mackerel and scad.  The fishing grounds are in the eastern and western Gulf of Thailand, inner Gulf, and the southern part of the Andaman Sea; the main ports are Samut Sakhon, Chonburi, Langsuan (Chumporn province) and Kantant (Trang Province).

              Luring purse seine (Uan Sung and Uan Tageang)

              Most purse seines in Thailand are used in conjunction with one of the two luring methods; fish shelter and fish luring lights.  A fish shelter (Sung) is constructed of bamboo poles, wire and coconut leaves, and fastened to a concrete block.  This luring method is used in day-time fishing.  Fish luring lamps (Tageang), which can be either electric or gass lamps, are used in night-time fishing.

              A luring purse seine is 400-800 m long, 80-100 m deep.  The main net has 20-25 mm mesh-size, the material is black nylon 210 d/4-12 and polyethylene 380 d/12-15 at the cod-end.  The float line is shorter than the sinker line (E=0.7-0.8/E=0.75-0.85).  The ratio between the depth and the length of net is 1/5 – 1/7.  The fishing boat is 18-24 m long (20-80 gross tons), with a 100-400 h.p. engine.  Thirty to forty fishermen are needed for an operation.

              The main catch are sardine, round-scad, selar-scad, and Indian mackerel.  Fishing grounds of fish shelter purse seine are in the central Gulf of Thailand (40-60 meters depth), while fish luring lights are used both in the Gulf of Thailand and the Andaman sea (20-40 meters depth).  Main fishing port for fish shelter purse seine are Pattani and Samut Prakan, whereas Chumporn, Prachuap Khirikhan, Phuket, Trang and Satun are the main fishing port for fish luring lamp purse seine.

              Fish schools are detected by sonar.  Fishing is done at nigh, usually in the central Gulf of Thailand, and sometimes in the South China Sea.  The catch comprises long-tail tuna, eastern little tuna, jack, trevallies, cavalla and others.  The fishing ports are in Rayong, Songkhla and Pattani.

              Tuna purse seine (Super seiner)

              During the past fifteen years (1982-1997) the most advance Thai fishing gear and methods is Tuna purse seine on the Super seiner. In 1987, the Department of Fisheries of Thailand has emploied one large fisheries research vessel, name R.V.Chulaporn. Her basic construction is trawler, then she was designed to be multipurpose of fishing with composed of stern trawler, longliner, gill netter and purse seiner. In 1994, The Southeast Asian Fisheries Development Center, Training Department has emploied a multipurpose fishery research and training vessel, name M.V.SEAFDEC. Her basic construction is Tuna Purse Seiner (Super Seiner) then longliner, gill netter and pot fishing were designed to work on for some cruise and some period. Then in 1995, Department of Fisheries, Thailand emploied a new Tuna Fisheries Research Vessel name R.V.Mahidol, she is a 1,270 gross tonnage super seiner, a typical type tuna purse seiner. Then, in 1998 Thai Off shore fisheries Association has emploied a used tuna purse seiner about 1,800 gross tonnage, she was also a typical tuna purse seiner, All most of them are operated in the Indian Ocean and Andaman Sea.

              Their fishing nets vary from 1,000 to 2,000 meters in length and 250 to 300 meters in depth and mesh size are 90 millimeters at bunt part and 210 millimeters at the body and wing, and all of them operate by fish aggregating devices, FADs or paayao. The target catch are skipjack, yellow fin and big eye tuna while their by-catch are rainbow runner, horse mackerel, leather jacket and dolphin fish.

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