of over 20 shew no selectivity in their distributions and that 

 in the Northeastern Sea Areap too,, the schools with a factor 

 of under 20 are taken in the greatest numbers along the Ogasawara 

 chain and the Zunan archipelago « although they are also taken on 

 the Sanriku coast o He foimd further that in the schools of fourth- 

 year fish having a condition factor over 20., the average body- 

 length and tlie average condition factor in the two areas are in 

 approximate agreements, and the variations from year to year in 

 the average body-lengths in the schools of fourth-year fish having 

 a condition factor of over 20 are in agreement for the two areasy 

 however J in the case of those under 20 they are not in Agreement » 

 Taking these facts into considerations he concluded that in the 

 Northeastern Sea Area the schools with a condition factor of over 

 20 are of the Ryukyu strain^, and those imder 20 are of the Ogasa- 

 wara strain, and that on the average for 193Uj 1935s and 1936 the 

 Ryukyu strain were 80 percent and the Ogasawar-a strain were 20 

 percent of the catcho According to the views of the persons 

 cited abovej, among the skipjack schools that migrate into the 

 Northeastern Sea Area^ those from the Ogasawara and Zunan Sea 

 Areas are comparatively few^ and the major part of them either 

 come north from the Satsunan Sea Area, or else are fish which 

 have moved north after first coming from somewhere to congregate 

 densely off Shikoku, in the Kumano Nada^, and off Zunano However, 

 these points need to be gone into a bit furthero 



If we try to summarize thq body-weight composition by fishing 

 grounds s as studied by Kimura^/ from the skipjack catchj we see 

 (table 1) that the composition varies considerably from one 

 ground to anotherc but in general small fish are numerous around 

 the islands off Japan proper j, while large ones are more numerous 

 around the islands to the south of Japano Furthermore <, mediimi= 

 sized fish are especially scarce in the Satsunan area and 

 especially plentiful in the northeasts and it appears at first 

 glance as if they moved north from Satsunan to the North- 

 eastern area, but if we compare the age composition inferred for 

 the Satsunan fishing grounds from the graph of body-length dis= 

 tribution given by AikawaJ/ with the age qonposition for the 

 Northeastern grounds obtained by Okarfloto£/ (table 2)s, one can 

 think that probably a part of age-group IV and almost all of age 

 groi:^) III and below migrate along the Kiuroshio to the waters 

 off northeastern Japano It is hard to determine, however, 

 whether "they come first to Satsunan and then move north from 

 there to the northeast through the waters off Japan proper., or 

 whether only a part of them go to Satsunan while the main body 

 of them go into Kinan^, moving north from there through the 

 waters off Japan proper, with a part of them turning south along 

 the way bat with most of them continuing on to the waters off 

 northeastern Japano 



k^ Kimxira. Kinosukei TheSkipjack Fishing Situationo Papers 

 on the Fishing Situation for the Important Species of Japan, 

 Part lo Lectures en Fisho Techo and Engo, Volo h^ 19Ulo 



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