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Abstracts list of Research
A STUDY ON FISHING METHOD AND UNDERWATER LIGHT PATTERN OF LIFTNET (BAGAN) IN INDONESIA.
(インドネシアにおける集魚灯敷網の操業方法と水中照度の検討)
°MULYONO S. BASKORO・SOKJIN CHOI・秋山清二・有元貴文（東水大）
[Objectives] Bagan is the coastal liftnet with kerosene lamps for fish attraction. It has a box-shaped net operated from the bamboo-platform which can be classified into 2 types; floated and fixed bagan. The aim of this research is to optimize the bagan fisheries in Indonesia; with special reference in underwater observation of fish behaviour and the profile of light intensity by kerosene lamp.
[Methods] The catch data of bagan fisheries during the period 1977-1994 was obtained from the Directorate General of Fisheries, Ministry of Agriculture in Indonesia. Underwater observation was carried out in Pelabuhan Ratu Bay, West Jawa, in August 1995. Portable fish finder was used to observe the fish behaviour during fishing operation. Transducer was set at the center of bamboo platform 1m below sea surface. Light distribution was measured using Underwater Lux Meter (OSK model 16648) and Digital Lux Meter (Minolta T-1M).
[Results] The historical transition of production, number, and CPUE of two types of bagan in Indonesia were studied. During 1977-1994, the floated bagan showed an increasing trend in production and CPUE, eventhough it's number was less than fixed bagan. The iso-lux contour pattern of 1 and 4 kerosene lamps were calculated according to the water transparancy and discussed with the schooling position of recorded images. The iso-lux contour pattern of 4 kerosene lamps is simple with the deep-oval shape of light intensity at maximum of 250 lux just below the surface to 0.1 lux near the net. The similar pattern of 1 kerosene lamp was observed, while the illuminated area was decreased by half to 4 lamps lighting. Fish school appeared between 9pm and 5am just below the lamp at the water column between 5m and 7m when the light intensity ranged from 1-10 lux . The school consisted of squid and small pelagic fish identified after hauling.
