fishery in the North Pacific between Japan 

 and Midway Islands. A relatively small part 

 of the Pacific albacore landings is there- 

 fore made up of fish taken in tropical 

 waters, and it is largely accounted for by 

 the mothership expeditions, and vessels 

 based in Samoa and New Hebrides. Consider- 

 ing the large numbers of independent long- 

 liners which exploit distant waters, it is 

 apparent that most of their effort is in 

 the Indian Ocean rather than in the Pacific. 

 This is more clearly seen when we examine 

 the catches of yellowfin in the Pacific and 

 the Indian Ocean. The Indian Ocean land- 

 ings, wholly made by independent longliners, 

 are generally greater than the Pacific 

 landings; the latter includes mothership as 

 well as foreign-based landings. 



Japanese catch in Indian Ocean 

 and Atlantic Ocean 



Following the opening of the Indian 

 Ocean grounds by the large independent long- 

 liners in 1952, landings of each species 

 increased. This increase was accompanied by 

 the exploitation of more and more grounds. 



If the catch records for any small area are 

 examined in detail, it is seen that catch 

 rates are high when a ground is first ex- 

 ploited and the catch rates decline as 

 exploitation continues. To compensate for 

 this Japan has been exploiting new grounds. 

 The fishing operations of this nation extend 

 over the entire tropical Indian Ocean. Due 

 to this steady expansion and the lack of 

 catch-location information the general de- 

 clining catch rates for specific areas are 

 not revealed by the over-all landings (fig. 

 19) . The catches increased until 1956 but 

 declined in 1957 • During latter years 

 greater effort was expended in the Pacific, 

 and the Atlantic was also exploited for the 

 first time. 



CATCH AND MOUNT OF FISHING 



Except for the information concern- 

 ing the yellowfin and skipjack of the east- 

 ern tropical Pacific, adequate biological 

 data to indicate the condition of the vari- 

 ous tuna stocks in the world are lacking. 

 Nevertheless, it is important to examine 

 such information as is available in order 

 to evaluate what these data portend. 



(SO 



125 



(00 



75 



50 



25 







75 



< X 



& 



in 



§ 50 



I 

 50 

 25 





 50 

 25 







I 



SKIPJACK 



ALBACORE 



■ ■■■■■■I 



YELLOWFIN 



BLUEFIN 



'*7-50 1951 1952 1953 1951 t955 /95i 1957 



It is necessary to remind ourselves 

 of some general well known phenomena associ- 

 ated with unexploited fisheries. By and 

 large, unfished populations will have a 

 significant proportion of large, old fish 



so 



25 

 



50 

 25 





 25 





 25 







INDIAN 



ATLANTIC 



BISEYE 



. _ - ■ ■ - 



BLUEFIN 



'*7-'50 1951 1952 1953 195* 1955 1956 1957 1957 



Figure 18. — Japanese catch trends in the 

 Pacific (1947-50 and 1951-57). 



Figure 19.— Japanese catch trends in the 

 Indian and Atlantic by species 

 (1947-50 and 1951-57). 



30 



