(a) Along the Northern Equatorial Currant past the RiilippineSy Taiwan, and 

 Okinawa to the Satsunan area and thence gradually northward„ 



(b) From the South Seas area to the Zunan area along the northerly warm 

 current of the-Kuroshio which originates in the waters near the Bonins 

 in the spring. 



(c) Northv/ard between the Northern Equatorial Current and the northerly 

 warm current of the Ogasawara region to the vicinity of the Kinan 

 reefs in the Kinan area (30° 10 « North, 136^ 4-5" East) „ 



These three are assumed to be the routes of migrationo These schools 

 of skipjack show a tendency to concentrate gradually in the Northeastern 

 area as the power of the Kuroshio increases from May to Julyo In the latter 

 part of April and the early part of May they congregate in a radius of 

 150 to 300 miles southeast of Nojima Saki (Chiba Pref ecture) „ Then these 

 schools move to the northeast and proceed north as the water temperatures 

 rise„ Every year in the middle and iaxter parts of July they reach the 

 area 150 to 200 miles east of Klnkazan (Miyagi Prefecture), Further 

 northward movement of the schools is barred by the pressure of tne O^faShio, 

 and they remain for s comparatively long time in these waterSo In 

 September they reach the northern limit of their migration which, depend- 

 ing on the year 5 may be as far north as the waters adjacent to the 

 Kuriles, that is, the vicinity of Etorcfu I„ and Shikotan I, Thereafter 

 as the Oyashio increases in strength the schools turn southward and 

 move south comparatively far out to sea, over 300 miles off shore, re- 

 turning to their native South Seas by way of the waters of the Zunan area. 



In the Amami Oshxma region of the Satsunan area, the schools appear 

 around the early part of February and are most numerous from the end of 

 February to around Julyo After that time they gradually decrease in 

 numbers and disappear about December „ Most of the schools in this area 

 come up from the south and remain in the area» Some of them take up 

 residence around tlie reefs and become the so-called "sedentary fish''^ 

 some part of thea eontisaue north, and the rest return to the south in the 

 autumn„ 



The schools which appear in the Kinan area are most numerous around 

 May, their numbers dimini':ihing remarkably in the latter part of June, 

 Possibly they move north into the Northeastern area. The schools of the 

 Zunan area put in their appearance first in the vicinity of Torishima and 

 are mos*. numerous in May and June, Thereafter they divide into schools 

 which migrate north into the Northeastern area and schools which remain 

 from s-ummer to autumn in this area,, A number of schools returning south- 

 ward from the Sanriku area are also seen in the Kinan area during October 

 and November o 



3, Conditions iriiich regulate the migrations of the skipjack schools 



The migrations of thi^ skiDJack schools are premised upon the strength 

 or weakness of the Kuro";.i.Oo The iiTater temperatures in the Kuroshio begin 

 slowly to rise in early February and reach their maximum around July and 



22 



