1.4 Tuna Purse Seine
Two types of tuna purse seine nets are used: the hybrid net which catches small pelagics and tuna in coastal and offshore waters, and the super seine net which is used in offshore and international waters where the major catches are skipjack, yellowfin and big-eyed tuna. The first type is operated on board vessels from 200 to 300 GT. The net measures 720-1080 m long and 144-250 m deep. The inshore tuna net uses 210d/30-48 in the body and wings and 210d/60-72 at the bunt portion. Mesh sizes range from 50.8-76.2 mm in the bunt section and 88.9-203.2 mm in the body and wing portions.
The second type is used in boats of 400 and above GT with refrigerated brine solution as standard for preserving the catch. The net measures 1,080-2,160 m long and 216-324 m deep. The offshore tuna net uses 210/60-168 in the bunt while 210/36-60 in the body and wings. Mesh sizes vary from 88.9-127 mm in the bunt and 76.2-254 mm in body and wing.
Night time fishing is largely done using anchored rafts or payaws to concentrate the fish. The floating section of the payaw is made of bamboo, steel pontoons or galvanized drums. One purse seiner may work with several payaws but fish one or two in one night using strong mercury lamps or superlights. Another technique being used to maximize fish concentration in one payaw is to pull five to ten payaw attractants or habong during the day into one central or terminal payaw. The concentration of fish increases in the central or terminal payaw due to fish accumulation from other attractants. It is then lighted at night and encircled by the catcher boat at dawn. It was estimated that such a technique increases catch by 20% to 30%. Payaws are lighted at dusk by the dim boat which has two-four 1,000 watt/bulbs. With a sufficient tuna school, the attractant is removed from the floating section, tied to the dim boat and allowed to drift away. The catcher boat then encircles the dim boat and completes operations until the catch is poured into the fish hold with brine solution. The fish is chilled and frozen to a temperature range of -15½ to –30½C.