also requested a record of stoaach contents, the isize of fish, and daily catch. 

 In looking at a table of measuremGiits, the lengths and weights of skipjack caught 

 by pole and line are small. The -^ir^ller ones vreighed about 200 momme (1.65 lbs,) 

 and the larger ones, from 300-4C0 momniQ (2,4. to 3.3 lbs.). Among the larger ones, 

 there were fish that v;eighed or;e kan (8.27 Ibs.)^ The catch in May was extremely 

 large so I thought that skipjack spawn possibly in April and May« Not too many of 

 the larger skipjack were caught by pole and line, and I believe that this is prob- 

 ably due to the fact that as the ovarj' enlarges, it presses against the internal 

 organs causing a loss in appetite. Furthermore, 1 believe this to be the solution 

 to the question why the possibilities of catching large mature skipjack decrease 

 during the spawning seasono I believe that research would be expanded if nets as 

 well as hooks were used to capture fish. At any rate, it would confirm the fact 

 that ovaries of skipjack are comparatively large from April on, reaching maturity 

 In May, In searching for spawning grounds, juveniles are collected and the sector 

 from which these are abundantly recovered is assumed to be the spawning area. If 

 a thorough investigation were made around Palau, I feel that the problem of skip- 

 jack spawning grounds would shortly be solved. 



Hatai : Thank you for your information. Next, 1 shall call upon Mr. Oshlma for dis- 

 cussion. 



Oshlma ; I am an Ichthyologist, but until recently ray work has been devoted prima- 

 rily to research on salmon and trout« I regret to say that my knowledge of skip- 

 jack and tuna is very limited outside of the few observations I made In the South 

 Seas when I was fonnerly in Formosa » At that time Dr. Kishlnouye, who was special- 

 izing on these fish, had his eyes set on the southern areas as spawning grounds for 

 skipjack and tuna. He requested that we watch for Juveniles during our study of 

 other families of fish. At one time we foi-warded some specimens to him which were 

 taken off the coast of Keelung, but these were all Scomberoides, more specifically, 

 a species of Chorlnemus . 



The salmon and the eel stop feeding entirely when they begin their spawning 

 migration. Consequently, eels descending towards the sea are not attracted by bait 

 placed in bamboo baskets set out to capture them. Because of such exaii4>les, Ur. 

 Manikawa*s statement that skipjack and tuna cannot be caught during the spawning 

 season may be true. The reason why skipjack with matured eggs cannot be caught in 

 May may also originate from such circumstances. However, according to recent re- 

 ports, skipjack of various sizes are taken throughout the year by the fishery in 

 British North Borneo, Numerous skipjack weighing about 100 momme (.82 lbs.) are 

 caught in the Sulu Sea around November; these constitute a nuisance because they 

 are not of commercial size. About 60^ of those skipjack caught In April and May, 

 however, are adults and the roe and testes from these fish are often canned, l&r. 

 Tsuji, the present managing director of the Borneo Fishing Co., Ltd., had these 

 products on hand at the time of my visit and he showed us a sample can containing a 

 large testis. These facts are clearly contradictor^' to the aforementioned concep- 

 tion that skipjack cannot be caught during the spawning season. It is possible 

 that juvenile and mature skipjack and tuna are not caught in waters adjacent to 

 Japan because this area is not a migratory sector for these particular sizes of 

 fish. 



Upon closely correlating the flow of the Kuroshio to the migration of skipjack 

 and tuna, it may be assumed that the originating point of the Kuroshio, wAiere the 

 Northern Equatorial Current touches the Philippine Islands and changes course to 

 \the northeast, is the spawning ground for migrator}' fishes. For example, the 

 Japanese mullet, found frequently along the coast of Formosa, descends southward 

 from the South China coast along the western coast of Formosa, spawns in the Bashl 



