From the Bulletin of the Japanese Society of Scientific Fisheries, 

 Volo 2, Noo 3, ppo 107"111„ September 1933o 



Types of Skipjack Schools and Txieir Fishing Qualities 



By 



MLchitaka ITda 

 (Fisheries Expei-inient Station) 



/'Siglish title and abstractj^ 



The Shoals of "Kat'uwo" and their Anglirig,, 



SINOPSIS 



The shoal of "Katuwo" /lathynnu s vagans (Lesson)/ is often 

 found associated with either sea-birds^ drifting timbersj vriiales, 

 sharks, or what noto The association with sea-birds, or whales 

 is almost characteristic to the shoals of this fish found in the 

 districts south to ProVo Bosy^ij whereas the shoals associated 

 with sharks are mostly distributed in the northern districtso 

 Such difference of the distribution corresponds to that of oceano- 

 graphical conditions^ particiilarly of salinity (FigSo 1^ 2 and 

 Tabo 1), 



The dcnseness of crowd and the degree of biting are represented 

 quantitatively with -^a index-numbsrs k and q respectively (TabSo 2 



and 3)9 vlZo, k s E,X-£liE » whare m and n are the number of records 



m f^n 

 of dense and thin crowds respectively, and 



q a 3p2 / 2p;^ ^ Pq ^ 0„5p-;^ / Oolp"2 s 



P2 / PI /^ Po / P"l / P-2 

 where p^, p, ^ p^^ p=^ and p"2 are the mimber of records of very 

 good^ S°odj mediuiTi, poor and very poor biting respectively„ The 

 index-number of fishing value of a shoal defined by-™_, whera 

 N'3 1 and t are the totjil nuinber of fishes angles 5, tSe number of 

 rods used and the duration of angling respectjvslys varies ivith 

 the product kq (Tab„ 6)0 But, since N» is not exactly proportional 

 to t (^Tahc 5) s "the above-mentioned index number is only an 

 approximate oneo 



The relation between the degree of biting of "Katuwo" and the 

 quantity of the contents of their stomach (Tab, ii) . seems to be 

 explained by taking the time required for digestion into account, 



/STnd of English abstract/ 

 68 



