(Koshonm Tokel), and for 1916-45 In the Statistical YearbookB of the Department of Agricul- 

 tar« and Forestry (Norin Toksl). As noted In the sections on veseels and gear, the Japanese 

 fishing operations for the tunas have been carried on primarily by two methods, surface pole 

 and line for the sKipjack, and long line for the remaining tunas and related species ^ . In 

 official goveraT.ent reports this breakdown has been followed without considering other gear 

 of l^Bser importance. The catch by species, moreover, has not been recorded. Two large 

 categories, skipjack and tuna, have been deeif^nated. All species of tunas (with the ex- 

 ception of the skipjack) and spearfishes are included in the category "tuna" regardless of 

 biological relationships. An undetermined amount of sharke may be included in the tuna 

 catch since they are sanetlaee taken on long lines. The data (republished in Eepenshade, 

 1947, Tables 3 and 7) are considered by Japanese fishery workers to be incomplete tut are 

 reliable to the extent that they Indicate trends in the development of the tur.a fisherleB 

 BUbeeqaeut to ]908 (Figure 22). 



A breakdown of the tuna catch into coastal and offshore categories prior to 1915 is 

 not available, ieglnning with 1915, however, this breakdown was made and continues to the 

 present with interruption only for the years 1941-43. The criterion eetnbliBhed for deter- 

 miniu,3i coastal and offshore categories has been the operating distance from shore 7/. In 

 actual practice the breakdown was aiado according to size of boat, horsepower, and resulting 

 ability to operate either near or at a distance from homo port. 



Following the introduction of skipjack and tuna long line motor-driven veseelB during 

 the first decade of the 20th Oentury, it became possible to exploit the coastal waters more 

 efficiently and also to extend the fishing grounds into more distant areas where greater oon- 

 centratlona of certain species such as the skipjack, the swordfish.- and the etriped marlin 

 were present. Thus the Japanese had the means and facilities for going further from shore 

 and eijianding the fisheries whenever increasing demand for various tuna products required 

 3uch expansion. 



The overfall production of tne fie,.ories after the beginning of World War I showed 

 a marked increase, a typical reaction to demand for food during a war^-lnspired effort. More- 

 over, the cumulative effects of the transition fronj sail and nand-powered boate to engined 

 vessels were betjinning to be felt in a fishery where the speed and maneuverability of the 

 vessel is of vital importance. By 1915 offshore fishing, especially for the skipjack, had 

 a noticeable effect on production, and by 1917 it had become more important than the inshore 

 operations (Figure 22). 



After 1915 the catch of skipjack In coastal waters began to drop sharply, and this 

 decrease continued until 1928 when the catch leveled off at a low rate. Various reasons may 

 be given for this trend. Among the more likely la a shift in fishing effort from coastal to 

 offshore waters or a possible change in the criterion used to determine Inshore and offsnore 

 categories. The movement offshore of the major concent rat icna of skipjack owing to changed 

 hydrographlcfil conditions, industrial pollution of inshore water, or heavy coastal boat traf- 

 fic is also possible. The reason most favored by the Japanese is changed hydrographical con- 

 ditions, but most of their fishery men are prone to explain decreases in production solely on 

 the basis of chan^^es in water temperature and to dlsregerd the contributing effects of other 

 important factors, such as technological development and Increased intensity of fishing effort. 

 Despite the marked decrease in the inshore catch, the skipjack fisheries as a whole wore able 

 to maintain their former level of production and to show an increased yield whenever the 

 occasion demanded it. 



Dleael en'/ines and steel boats Increased efficiency of operation for the offshore 

 fisheries in the years following these innovations. Thin Is reflected in a significant up- 

 ward trend in the amount of tuna caught during the late 1920' s. The increased catch not only 

 was the result of increased demand, coupled with ability to make large catches, but also was 

 accounted for by gradual extension of profitable fishing operations into waters at a distance 

 from the Japanese mainland. For example, the region near the Bonin Islands, to which a Japa- 

 nese-based skipjack vessel had first gone in 1908, now could fi/;ure importantly in the tuna 

 fisheries. 



£/ See pp 32 and 34 



2/ See footnote 4/ , p 37 



U8 



p-6307 



