From the Bulletin of the Japanese Society of Scientific Fish©ri.es, 

 Voio 3s Noo hf PPo ly6-202. November 193ho 



Local Variations in the Ccmposition of Skipjack 

 (Katsuwonas pelands ) Schools 



by 



Michitaka Uda and Jir5 TsukusM. 

 (Central Fisheries Experiment Station) 

 ^glish title and synopsis/ 



LocaT variations in the Composition of Various Shoals of "Katuwo", 

 Euthynnus vagans (Lesson) ^ in Several Sea-districts of Japan 



Mititaka Uda and Ziro Tukusl 



SYNOPSIS 



A study of the fisheries of "Katowo'S Euthytinus yagans 

 (Lesson), in several sea districts adjacent to japan xn 193^« 

 leads to some interesting results concerning their shcalxng 

 conditions — associated objects such as biras, sharks ^ yl^^les, 

 Simnrtimbers or what not; whether they are attached to banKs 

 S no4 denSness or cro.'ding| degree of biting, index of anglxng, 

 and the siz.e of individuals, which is classified xnto large (over 

 7-^Tr y^)]'E lbs J medl'xm (I088 to 3o75 k^c wt.) /U to 8 Ibs^,, 

 id sSil^lesi tian-lo88 kg„ wt„) ^^der h lbs J. sijes »- xn 

 Slatfon to the frequencies =f thsir appearances and the sxze of 

 catches 



Fron- the studv, for each sea-district, of the months, in which 

 the maximum percentage catch of fishes of each size^-roup, above men- 

 tioned, is attained in the fishing seasons the following results 

 of discussions on the migration of "Katuwo" will be given; (1) The 

 shoals, consisted mainly of fishes of medi-om size^ migrated in 

 1933 from the southern to the northern sea-district from sprxng 

 to summer, accompanied, in consequence, by the mc^ement cf their 

 fishing grounds/ (2) On the other hand, it can be noticed that 

 the local groups found around the banks in southern sea-dxstrxcts 

 consisted of comparatively high percentage of fishes of large and 

 small sizes in addition to those of medium sizso 



Ihe composition of various shoals of "Katuwo" in each sea- 

 district has some respective pecrliaritvo In the northern sea- 

 district the shoals are mainly associated with sharks or without 



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