present on the caudal region. Pelvic flna are either very thin ana elongated or are miss- 

 ing. All species attain gigantic si«e and are highly prised ty sport fishermen for their 

 fighting qualitlea. In Japan, however, the sailfish, awordfioh. and the aarllna are fished 

 only by commerolal methods. Little Is known ahoat the Mology of theee species. 



As stated previously, the Japanese research on the oceanic fishes reflects the com- 

 mercial importance of each. Hesum^s of the available knowledge on the four most important 

 species follow. These species, the skipjack, the black tuna, the albacore, and the yellow- 

 fin tuna, are virtually the only ones for which biological Information of any consequence 

 has been obtained. 



SKIPJACK 



Kateuwonus pelaais (linnaeus) 



Katsuo, Eatsuut Mandara, Magatsuo 



1. Oeneral 



Bvldence Indicates that the skipjack has, from ancient times, been an imoortant 

 article of diet for the Japanese people. Prehistoric remains of skipjack bones have been 

 found, along with those of the black tuna and other species, in shell mounds excavated in 

 northeastern Honshu. Since hooks, spears, and sinkers made of the horn or bone of land 

 animals were occasionally found beside these bone remains, it is aasomed that the ancient 

 people took the skipjack either by angling or by spearing when it entered shallow coastal 

 waters. 



The oldest recorded reference to the skipjack Is in the Kojlkl, written about 712, 

 in which it Is stated that the »katsuo" (hard fish) was dried on the roofs of the fisher- 

 men's homes. According to the Hippon 'Shoki, published in 720, the sklpj»«k was eaten raw 

 at that time. In the Engishlkl, a classical work on court ceremonies published in 907, 

 the skipjack was described as being caught in the waters off Mle, Shly.uoka, Eanagawa, Chiba, 

 Kochi, Miyazaki, and Wakayama prefectures (Tamamoto. 1942, pp 138-143). A variety of foods 

 were prepared from it, many of which were given to the government and court as tribute. 



During the time of the Tokugawa Shoguns (1603-1867) extravagant prices were paid 

 for the quick delivery at Yedo (Tokyo) of the skipjack taken In the late spring, the season 

 during which the fish was in prime condition for being eaten raw. Thus the skipjack has, 

 from early times, been a highly prized fish, and even today the Je^anese consider it the 

 most valuable of the pelagic species. 



The skipjack fisheries were restricted to coastal waters until the development 

 of motor-driven vessels permitted the gradual extension of the fishing grounds from the 

 shore to the open sea. The great demand for this species was sufficient incentive to 

 warrant extending the fishing grounds until, in the northwest Pacific region, they reach 

 a distance of almost 600 miles from the Jfqjanese coast. Thus the shore fishery has de- 

 clined in relative importance, and the offshore grounds, which contain the larger popula- 

 tions of skipjacks, now supply the bulk of the catch. 



2. Diagnostic Characteristics 



The skipjack (Figure 5) may be recognized by the four or more dark, longitudinal, 

 bands against the white pigment on the lower half of the body. The back Is dark bluish 

 violet, with some faint transverse light-colored markings on the posterior half. All fine 

 are dusky In e^pearance although the second dorsal, anal, and caudal are lighter than the 

 others. The body Is pluii^, sharply pointed, and almost circular in cross-section. The 

 skipjack la naked except for a corselet of scales found in the region of the anterior fins 

 and a few Islolated, minute scales scattered over the remainder of the body. 



3. Distr i bution and Migration 



Although data on the ekipjeck are more complete than for any of the other scombroid 

 fishes, the Japanese literature contains few precise startements regarding its distribution 



13 

 p-6307 



