168 EIGHTH PACIFIC SCIENCE CONGRESS 



Hiyama wants to add, seeing Nakamura's distribution maps, that 

 this species has less tendency o£ southward migration shown in the fore- 

 going two species, and that the thick distribution is found in the area 

 more influenced by the coast, or by the existence of islands or lands. 

 Hiyama and colleagues are now working on the morphometry of the 

 above-mentioned four species after the method used by U.S. biologists, 

 but it is still too early to report the results. 



Neothunnus rams. As the catch by the Japanese fleet is not enough 

 to indicate the distribution and migration, the only fact that Nakamura 

 can see is that this species is distributed in the area near the Indo- 

 Australian Archipelago, with its northern limit at the Ryukyu Islands. 

 Istiophoridae. Tetrapturus angustirostris has remarkable oceanic 

 character in general and is thinly distributed in the tropical and sub- 

 tropical area. A thick fishing ground appears usually off the east coast 

 of Formosa from November to January. 



Istiophorus orientalis has wide distribution in the West Pacific, 

 having a rather coastal character. The center of the distribution is 

 thought to be in the Indo-Australian Archipelago, and its northern 

 limit is in the North polar front. From May to August a thick fishing 

 ground appears near the Philippines and Formosa. Kajikia mitsukurii 

 has more oceanic character than the former, and has also a wide dis- 

 tribution extending to the North Pacific, with its center at subtropical 

 convergence. The dense fishing grounds appear at 30-40°N in autumn, 

 and moves south in October. And from March to June the dense 

 group of the grounds appears in 20-30° N. After K. mitsukurii went 

 down south, fishing grounds in 30-40°N are occupied by X/j^/?/a5 gladius. 

 The distribution of K. jormosana is not yet well known. Eumakaira 

 nigra has a remarkable oceanic character, distributed in tropical and 

 subtropical area. This species has its distribution range south of that 

 of K. mitsukurii. This shows a northward migration from May to 

 July, v^^ith its northern limit at subtropical convergence, and reaches to 

 20-26 °N zone nearly one month later than K. mitsukurii. The female 

 of this species is always bigger than the male. The latter rarely exceeds 

 100 kgm. in weight, so the size composition of the catch should be con- 

 sidered based upon the sex ratio of it. Marlina marlina is confined 

 within the coastal area of the Indo-Australian Archipelago, as already 

 indicated. This also has a size difference between the sexes, the male 

 rarely exceeding 120 kgm. Xiphias gladius is thought to have world- 

 wide distribution, but in the Northwest Pacific the dense distribution 

 is recognized by Nakamura at the North from subtropical convergence 

 beyond 43°N. In August a good fishing ground is usually formed in 

 150-155°E, 40-43°N, which moves south thereafter, just like Germo 



