1.3 Morphology 



1.31 External and internal morphology 



Description of adult (after Nakamura et al. 1968): 



First dorsal fin rays 38-42, second dorsal fin rays 6- 

 7, first anal fin rays 13-14, second dorsal fin rays 6-7, 

 pectoral fin rays 19-20, pelvic fin 1, 2. 



Body elongated (greatest depth of body 3 about 4.8- 

 5.2 in body length), slightly compressed laterally 

 (width of body at origin of pectorals about 11.0-13.4 in 

 body length). Snout long (bill length about 0.95 in 

 head length) with a cross section nearly circular. 

 Scales distributed densely on body surface; scale ends 

 pointed and long. 



Rasplike teeth on jaws and palatine. Lateral line 

 obscure but consists of a single line. Head large (head 

 length about 4.0-4.2 in body length). Eye moderate in 

 size. Posterodorsal part of the head between preor- 

 bital and origin of the first dorsal fin strongly convex. 

 Caudal fin large and strongly falcate. A pair of keels 

 situated a little posteriorly on caudal peduncle. Pec- 

 toral fin situated low on body, long (length of pectoral 

 fin about 1.1-1.3 in head) and its tip pointed. Pectoral 

 fin extends stiffly away from the body, cannot be fold- 

 ed back against the side of the body. First dorsal fin 

 starts above supraposterior margin of the opercle and 

 ends just before the origin of the second dorsal fin; 

 anterior portion lower than the body height and 

 gradually decreasing in height posteriorly. The tip of 

 the anterior part of the first dorsal fin pointed. First 

 anal fin large and triangular in shape, its tip pointed. 

 Second dorsal fin nearly equal to second anal fin in 

 size and shape, origin opposite each other, or the 

 former a little farther forward than the latter. Pelvic 

 fin shorter than pectoral fin. 



Membrane of first dorsal fin dark blue, other fin 

 membranes brownish black. No marks or blotches on 

 the body. Dorsal part of the body blackish dark blue, 

 ventral part of body silvery white. Color of the body 

 fades after death, so this species is called "Shiroka- 

 jiki" (= white marlin) in Japan. While alive, the color 

 of body is tinged with black, and hence this species is 

 called "black marlin" in English-speaking countries. 



Nasal rosette composed of about 50 laminae. Gonad 

 symmetrical. Anus situated just anterior of the origin 

 of first anal fin. Skull broad and strong; the preorbital 

 part elongated and its postorbital part shortened. 

 Ventral part of the vomer and anteroventral part of 

 the parasphenoid flat. Temporal ridge parallel with 

 pterotic ridge. Haemal and neural spines of the cen- 

 tral part of vertebrae high trapezoid in shape. Lateral 

 apophysis well developed but not so much as in 

 Makaira mazara and M. nigricans. Vertebrae 11 + 13 

 = 24. 



'Measurements were carried out by the method of Rivas (1956). 



2. DISTRIBUTION 



2.1 Total Area 



Black marlin are distributed widely in the Indian 

 and Pacific oceans; very few catches have been 

 recorded from the Atlantic Ocean (Fig. 2). Only stray 

 black marlin seem to invade the Atlantic Ocean by 

 way of the Cape of Good Hope; possibly breeding 

 stocks do not exist in the Atlantic Ocean. Good com- 

 mercial fishing grounds exist in the East China Sea, 

 around Formosa, in the waters off northwest 

 Australia, the Arafura Sea, the Sulu Sea, the Celebes 

 Sea, and the Coral Sea. Good sport fishing grounds for 

 black marlin are found in Pinas Bay of Panama and 

 off Ecuador (Fig. 3). 



Sea surface temperatures at or near the areas where 

 the black marlin are caught range from about 15° to 

 30°C (Howard and Ueyanagi, 1965). 



2.2 Differential Distribution 



2.21 Spawn, larvae, and juveniles 



Very few larvae have been obtained from the 

 tropical western north Pacific, tropical Indian Ocean, 

 and tropical water off northwestern Australia and the 

 Coral Sea (Ueyanagi, 1964). It has been surmised that 

 the spawning grounds are in the northwestern part of 

 the Coral Sea (Ueyanagi, 1960; Ueyanagi and Yabe, 

 1960) and in the vicinity of Hainan Island, South 

 China Sea (Nakamura, 1941, 1942). But spawn is not 

 identified. 



2.22 Adults 



This species is distributed widely in warmer parts of 

 the Pacific Ocean and the Indian Ocean and densely 

 in coastal waters. In tropical open seas areas, distribu- 

 tion is very scattered but continuous, whereas in 

 temperate open seas, there is almost no occurrence of 

 this species (Howard and Ueyanagi, 1965). In tropical 

 open seas areas, there is a tendency for this species to 

 occur in the vicinity of islands (Nakamura, 1953; 

 Royce, 1957; Koto, Furukawa, and Kodama, 1959; 

 Ueyanagi, 1963). 



2.3 Determinants of Distribution Changes 



In the East China Sea, black marlin fishing 

 grounds, which are shallower than those of the other 

 billfishes, are found in the areas where the Kuroshio 

 and Tsushima currents are mixed with the waters of 

 the Yellow Sea (Koto et al., 1959). Optimum 

 temperatures for harpoon fishing of black marlin 

 westward of Uotsurijima in the East China Sea, are 

 23° to 25°C between October and April (Morita, 1952). 



2.4 Hybridization 

 No data. 



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