5. EXPLOITATION 



5.1 Fishing Equipment 



5.11 Gears 



Tuna longlines are employed to catch black marlin 

 in most fishing grounds where this species occurs; 

 areas include the East China Sea, the Sulu Sea, the 

 Celebes Sea, and the Coral Sea. Harpoon fishing is 

 carried out in the fishing grounds of Taiwan and 

 southern Japan. Sport fishing using trolling gear 

 catches many black marlin in Pinas Bay, Panama and 

 off Ecuador. 5 Sometimes this species is caught by set 

 net used to catch yellowtail in the Japan Sea. 



5.12 Boats 



The black marlin is mostly caught by ordinary tuna 

 longliners. The vessels of the longline fleet vary con- 

 siderably in size; the largest are about 1,900 tons with 

 several small catcher boats stored on each side of the 

 deck. Longline vessels are constructed of wood or 

 steel; those of more than 100 gross tons are usually of 

 steel. Most of the longliners are 250 to 350 gross tons; 

 at this size they appear to be the most economical and 

 efficient to operate (Yoshida, 1966). 



Small wooden boats are employed for harpoon 

 fishing in Taiwan and southern Japan. The wooden 

 boat is about 10 m long, and is powered by a small 

 engine. 



Ordinary trolling motorboats are employed for troll- 

 ing in the sport fisheries of Panama, northeastern 

 Australia, and Ecuador. In these areas black marlin 

 are caught more frequently than in other sport fishing 

 grounds for tunas and billfishes. 



5.2 Fishing Areas 



5.21 General geographical distribution 



The black marlin is distributed widely in the 

 tropical and temperate waters of the Indo-Pacific, but 

 more restricted in the Atlantic (Fig. 2). The species is 

 taken commonly by tuna longline as a by-catch. The 

 species is densely distributed in the vicinity of islands 

 and in coastal waters. The most important commer- 

 cial fishing grounds are in the East China Sea, the 

 waters around Formosa, the waters around northwest 

 Australia and the Coral Sea (Figs. 2, 3). 



5.22 Geographical ranges 



Spawning stocks of this fish are believed to be con- 

 fined to the Indian and Pacific oceans. Specimens 

 stray occasionally into the Atlantic Ocean (Fig. 2). 

 From commercial fisheries data the northern limit is 

 about lat. 40° N in the northern Pacific Ocean and 



■■Recently Cairns, Queensland of Australia has become famous for 

 trolling of black marlin. 



about lat. 45° S in the southern Pacific Ocean and the 

 Indian Ocean. In the southern area off Tasmania, the 

 limit extends to lat. 50°S (Fig. 2). 



5.23 Depth ranges 



The commercial longline fishery is generally con- 

 ducted in waters over 100 m deep. In the equatorial 

 western Indian Ocean, peak catch rates of black 

 marlin have been reported to occur at the 201- to 500- 

 fathom depth range (Merrett, 1971). The swimming 

 layer of this species is usually considered to be 

 shallower than those of other species of billfishes. 



5.24 Condition of the grounds 



Most areas exploited at present are coastal water, 

 but the grounds are various. 



5.3 Fishing Seasons 



In the East China Sea from lat. 30° to 34°N the 

 fishing season begins in July and ends in January 

 (peak in August, September, and October); from lat. 

 25° to 30°N the fishing season occurs from May to 

 July and October to April with peaks in June and Ju- 

 ly, and October and January (Koto et al., 1959). 



The fishing season begins in October and ends in 

 April (peak in November and December) near Uo- 

 tsurijima in the East China Sea (Morita, 1952). The 

 fishing season around Formosa extends throughout 

 the year; the peak occurs between October and 

 December in the South China Sea, and in February 

 and March off eastern Formosa (Nakamura, 1953). 



5.4 Fishing Operations and Results 



5.41 Effort and intensity 



In all of the areas, there is insufficient data on effort 

 and intensity of commercial fishing for this species. 

 However, it is known that most of the effort and inten- 

 sity occurs in the East China Sea, the waters around 

 Formosa, the waters around northwest Australia, the 

 Coral Sea, the Arafura Sea, the Sulu Sea, and the 

 Celebes Sea. 



5.42 Selectivity 

 No data. 



5.43 Catches 



Catches by Japanese tuna longliners for 1962 to 

 1970 are given in Table 3. 



6. PROTECTION AND MANAGEMENT 



6.1 Regulatory Measures 



6.2 Control or Alteration of Physical Features of 

 the Environment. 



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