14° and 18°S. The major source for recoveries is the Pacific-wide 

 Japanese and Korean commercial longline fishery catch, and, to a 

 minor extent, the catch of Australian and New Zealand commer- 

 cial and recreational fisheries. Few recoveries could be expected 

 from the billfish recreational fishery since the numbers of billfish 

 taken are small compared with the catch of the commercial long- 

 line fishery (avg. 9,100 fish, 1969-78, Japanese longline data). The 

 recreational fishery operates in a relatively restricted seasonal and 

 geographical area near the edge of the Great Barrier Reef where 

 the resource is available and catchable, and high rod-and-reel 

 catch rates can be obtained. Potential recovery areas by anglers 

 are generally restricted to the major tagging areas. The longline 

 fishery, however, samples over a large area of the ocean and it is 

 possible that recoveries could be made throughout the year, some- 

 times at considerable distances from the location of tagging. The 

 extensive Japanese longline fishery recovers the most tagged 

 marlin. 



Black marlin are distributed widely throughout the Pacific and 

 Indian Oceans with some catches reported in the South Atlantic 

 Ocean. Some of the better longline fishing areas for black marlin 

 are in the east China Sea near Taiwan, off northwest Australia, 

 the Arafura Sea, Sulu Sea, Celebes Sea, and the Coral Sea off 

 northeast Australia. Of interest to this migration study is that no 

 longline effort or catches of black marlin are reported north of 

 Australia in the eastern Arafura Sea. Between Cape York, 

 Australia, and Papua lies the Torres Strait, a large area having a 

 water depth of < 20 m. This shallow area may inhibit the migra- 

 tion of black marlin between the Coral and Arafura Seas. The 

 distribution of black marlin as inferred from catch rates from the 

 Japanese longline fishery in the Pacific, Indian, and South Atlan- 

 tic Oceans is given in Figure 1 . 



Black marlin have been an important resource to the Japanese 

 commercial longline fishery in the western Pacific since the early 

 1950's. Catch levels of all fleets in the western Pacific are currently 

 about 3,000 t (metric tons), approximately one-half the peak 

 catch in 1957, with about 59% of the southwestern Pacific black 

 marlin catch being taken in 1976 by Japanese longliners (FAO 

 1979). 



While the longline fishery generally targets on the tunas, in cer- 

 tain areas of the Pacific they may target upon marlin, sailfish, 

 swordfish, or both tunas and billfish. Billfish comprise about 

 18% of the total longline catch in the Pacific (Ueyanagi 1974). 

 However, the ex-vessel value of some species of billfish, such as 

 striped, blue, and black marlin, may be two or more times that of 

 some tunas, making the fraction of billfish an important factor in 

 determining the location of fishing effort. Black marlin appears to 

 be a target species in the western Coral Sea near the tagging area 

 during the spring and early summer months of September 

 through January. The distribution of longline fishing effort and 

 catch rates obtained in the areas to the south, west, and north of 

 the tagging area, in months subsequent to tagging, is an important 

 factor in evaluating tag recovery data. 



METHODS AND EQUIPMENT 



All black marlin tagged in the Pacific under the auspices of the 

 Cooperative Marine Game Fish Tagging Program were caught by 

 anglers using rod-and-reel, and were tagged and released by the 

 angler or a member of the charter boat crew. Several types of tags 

 were used in the 1960's, the principal type being the double barb- 

 ed, all-plastic FM67 tag (Fig. 2). Other tags used in small numbers 

 included the Type "A" tag, a metal-tipped tag similar to the "H" 

 tag, and type "B" tag, a small, single-barbed plastic tag similar to 

 tags currently being used for tunas (Fig. 2). Since 1970, the tag 

 distributed has been the stainless steel dart tag ("H" type). This 

 tag has a nylon monofilament line extending from the stainless 

 steel barb, with a yellow polyvinyl tubing sleeve over the 

 monofilament for printed information. Numbers and letters on 

 the yellow polyvinyl sleeve are heat embossed in black, giving the 

 tag's serial number and return and reward information. All tags 

 furnished by the National Marine Fisheries Service were manufac- 

 tured by the Floy Tag and Manufacturing Company, Seattle, 

 Wash. 



Each tag is attached to a postcard having the tag's serial 

 number printed on it. After tagging a fish, the angler completes 

 the information requested on the postcard such as tagging date, 



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