As has already been said several times, although the centers of distribution of these 

 fishes vary somewhat, they are essentially warm-water animals and consequently most of them 

 occur at all times in the waters of the low latitudes. In the case of the black tuna, the albacore, 

 and the broadbill it appears that the center of their distribution lies in rather high latitudes. In 

 any case, none of these species leads a sedentary life within a narrow area of the sea, but they 

 all move through extremely broad reaches of the ocean. The fishing grounds and fishing seasons 

 change in response to these movennents. 



Looking at the situation in Japanese waters, we see that from spring to summer the 

 Japan Current (Kuroshio) increases in strength, so that warm sea water is brought far to the 

 northward, at the same tinne all of the seas of the northern hemisphere grow warmer, and the 

 tunas and spearfishes gradually move toward the north. The reverse occurs from autumn to 

 winter, when the temperatures in the northern hemisphere gradually fall, accompanied by a re- 

 turn to the south on the part of the fish. The outlines of these movements will be set forth below, 

 but in recent years the patterns of migration have undergone much change, the black tuna, for 

 example, scarcely appearing in the coastal waters of Japan and no mass migrations of this 

 species being seen at all. 



In the waters of Hokkaido the black tuna generally appears in July. At about that time 

 the area 20 - 40 miles south southwest of Erimozaki becomes a good fishing ground. By Septem- 

 ber the schools are usually densely congregated within 30 to 40 miles of the coast from south of 

 Kushiro to Erimozaki. In October all of the offshore waters between Erimozaki and Ezanmisaki 

 are fishing grounds, but from this nnonth on the fish finally begin to disappear fronn this area. 

 Thus the fishing season on the Hokkaido coastal ground is from July to October, but in recent 

 years there has been hardly any catch. The longline catches in this area are almost entirely 

 composed of black tuna, other tunas and spearfishes being alnnost completely absent from the 

 catch and only a few sharks being taken. 



In the offshore waters fronn Iwate Prefecture to Fukushima Prefecture, the so-called 

 Sanriku region, the fishing season is longer thaji in the Hokkaido coastal areas. In some years 

 black tuna are taken as early as April, but the season of greatest catch is the 3 months from 

 June to August. Thereafter the fish gradually disappear, but around Novennber they again begin 

 to be caught and scattered catches are made until around January. The fish taken fronn June to 

 August ajre called "ascending fish," while those taken after November are cjilled "descending" or 

 "returning fish. " In these waters striped marlin are taken in fairly large numbers during the 

 summer and broadbill are numerous in the winter. In some years bigeye tuna are also abundant. 

 Furthermore, during two seasons, in the sunnmer and winter, an extremely large number of 

 rakudazame ( Isurus nasus ) are taken by the so-called mokanawa longline fishery. 



Off the east coast fronn Ibaraki Prefecture to Chiba Prefecture, black tuna, bigeye 

 tuna, albacore, cind broadbill begin to be taken around Novennber and catches continue to be made 

 until around April of the following year. In the summer the composition of the catch changes, the 

 striped marlin and black marlin increase, and at the same time quite a few yellowfin are taken. 



Farther to the southwest in the waters from the Izu Peninsula to the Izu ShichitS 

 islands black tuna begin to be taken around November, the season at which they are caught most 

 abundantly being from January to February. In some yesirs scattered catches are also made in 

 April and May. Bigeye tuna are also taken at about the same time, but their fishing season be- 

 gins about a month earlier and lasts about a month longer than that for the black tuna. It appears 

 that albacore begin to be taken in some numbers on the longlines around March to May. In early 

 years the yellowfin begin to appear around April and are taken in greater or lesser amounts until 

 November. Striped marlin occur almost throughout the year, but they are nnost abundant from 

 June to September and are mainly taken with the harpoon. The fishing season for black marlin 

 appeeirs to begin about 1 nnonth later than that for striped marlin. The broadbill are most abun- 

 dant in the winter, the season being centered around January and February, with the center of 

 their fishing grounds lying to the east of the Shichito islands. 



28 



