o 



145 E. in January appears to have moved to the southeast, with a good fishing ground in the 



vicinity of 28 to 31 N. , 144 to 149 E. Between 150 and 160 E, there appears an area of 

 high catch rates in the vicinity of 32 to 34 N. , roughly in the center of this area, while some- 

 what to the south good fishing is also Indicated around 26 to 27 N. The position of the fishing 

 grounds at the center of this group la about 2 south of where it was in January, The question of 

 whether these fishing grounds are connected or isolated cannot be answered because the data are 

 scattered geographically. On the whole, fishing conditions ea^t of 160 E. longitude show a 

 distinct tendency to deteriorate from the levels reached in December and January. 



Chart £ (March), shows fishing generally much poorer than it was in February. The 

 areas with high catch rates have shifted farther to the south than they were in February, with 

 the principal fishing grounds between 27 and 30 N. latitude. The fishing grounds south of 

 Shionomisaki have shifted to the southeast and their center is in the vicinity of 28 to 30 N. , 

 136 to 139 E. Between 140 and 150 E. there is a fishing ground with rather high catch rates 

 in the vicinity of 28 to 31 N. Eastward from 150 E. longitude to 165° E. there are hardly any 

 data and the distributional pattern is not clear, but what data there are show a strongly fluctuating 

 fishing situation with unstable catches. East of 165 E. the data are almost entirely confined to 

 latitudes south of 30 N. , and fishing is notably poor in connparison with February. The varia- 

 tion in catch rates between fishing operations is great and the catch is unstable. 



The end of the longline fishing season in this area is around the end of March or the 

 beginning of April, and jdmost no fishing is done aifter that time so there are practicadly no data. 

 If however, we look at the few data we have for the period April to July, we see that from time 

 to time during this period there are rather high catch rates and therefore we cannot believe that 

 the albacore have entirely disappeared from the area. Because of the extreme paucity of the 

 data, however, we cannot grasp the overall distributional pattern by means of longline catch 

 rates. 



During the summer albacore are teiken alnnost entirely by pole and line. As a result 

 the area covered by the fishing grounds coincides approximately with the fishing grounds for 

 skipjack. As the fishing method employed at this season is completely different, it is not possible 

 to make any comparisons of the density and pattern of distribution based on catch rates. Further- 

 more, the fish which are sought are generally for the most part young fish differing in size 

 from the albacore taken in the longline fishery. 



8/ 

 Un(>- has discussed the age composition of the albacore catch landed at Misaki in the 



summer. TJda— has hypothesized the migrational routes for the albacore shown in the figure on 



the basis of the changes in the fishing conditions and the size of the fish taken in the longline and 



pole and line fisheries in 1935 jind 1936. (The figure referred to has been omitted.) 



The albacore taken by longlines during the winter from the waters of Japan's east 

 coast to the area of Midway Island are thought to differ in size from area to area. In other words, 

 it is thought that different age groups migrate within different regions. There are, however, data 

 which indicate that there are rather marked variations from year to year in the size of the fish 

 and in their growth amd reproduction, and that fish of the same size are not always necessarily 

 taken in the same fishing ground at the same season. 



In the data used in preparing this book, records of the size of the fish taken are very 

 few, and for this reaLSon it is difficult to clarify the differences in distribution and the migrational 

 patterns of the fish by reference to their size. Consequently, I have only been able to discuss 



8^/ Uno, Michio. Connposition of the catch of the tuna pole and line fishery east of CaoeNojima. 

 Bull. Jap. Soc. Sci. Fish., Vol. 4, No. 5, pp. 307-309. 1936. 



9^/ Uda, Michitaka. The relationship of albacore fishing conditions to oceanographic conditions. 

 Bull. Jap. Soc. Sci. Fish., Vol. 5, No. 5, pp. 295-300. 1937. 



144 



