Notes la both tlie Zun3,r.i. and Satsunan S'-;a areas the number 

 of occurrences of sparse ocb.-.:us 'exceeds .Uiat cf dense schools. 



Note? (a) This sort of dictribution results froai the 

 fact that the distribution cf th.e objects ttI th which the schools 

 are associated varies depeadirg en the ares, and cceanographis 

 conditions. It must be that as the skipjack schools move into 

 various sea areas they es^ociate thsiiselve? successively Kith 

 different objectse 



(b) It is thought that the particular abundai'ioe cf 

 dense schools in the Northeastern Sea Area is due to the presence 

 of current bo-,mdarie3 where the -vrater cf the cold current system 

 tries to bloci*. the extension cf the waters of tiis warm c'jrrent 

 systenio 



(c) Howeverp ths gj-^eatsr number of dense schools 

 and the grear^er number of fish taksn in this sea area in mid- 

 summer in comparison -JriLth other sea areas is general throughout 

 the areao 



d« The next chai-acteristic of this sea area to be taken 

 up is the fact t25.at the skip.iack schools uite fax' 

 better than they do in the Zunan and Ogasawara sea 

 areas. It is a generally teorrn fact that ths schools 

 bite poorly in sea areas where there is too much 

 natural focdo Where plankton c-onsisting of diatoms 

 and noctiluca is toe abundantj, the schools bite poorly^ 

 but in areas whare the diatoms are comparatively scarce 

 and ths plankton consists c>iiefly cf flagellates and 

 radiclarians the fish sometimes bite well. 



X X X x X 



(k) Sources cf the s kipjack schools of ths Northeastern 

 Sea Areo. 



a. Among the schoclc from which skipjack are t£.ken by the 

 hook and line fishery in ths Northeastern Sea Ar^ea 

 fish cf li5 - >5 cm body length are extremely n'onerous 

 and as far as age is concerned fish in their fourth 

 year are abundant. Tnere are two different groups^ 

 migratory schools of fat fj.3h (ccnditicn factor over 

 20) and sedentary schools of lean fish (ccnditicn 

 factor under 20). 



Notes? (a) The t/erm "sedentary schocls" (island-bound 

 skipjack) is applied to those fish whose way. of life is closely 

 bo^md to small islands and shoals. The sedentary schools are 

 caught in ths greatest numbers as thsy move along ths Ogasawara 



11 



