therefore the catch has increased even in poor years, a con^aarison with 

 the average catch per boat per trip was made and failed to show any clear 

 correlation, but it does appear that fishing is good around the time when 

 the number of sunspots reaches its maximum and minimimio 



eo Relations with Other Marine Animals 



It is difficult to study the relations between the tuna and the other 

 marine animals which are taken with it because there is little data on 

 anything other than the broadbill swordfisho In years when many skipjack, 

 albacore, broadbill, and marlin are mixed with the catch the fishing for 

 tuna is poor, large tuna being particularly scarce ^ Skipjack were taken 

 in large numbers by tuna gear in 1927 and 1928, and albacore were taken in 

 1927, 19285 and 1929, being most numerous in 1928, The rate of appearance 

 of broadbill in the catch per 100 tuna was 0.8 in 1926, 66 in 1927, 3,8 

 in 1928, 1,2 in 1929, 3ol in 1930, and 2,1 in 1931, When the broadbill 

 were numerous, the tuna fishing was poor, Ihis is shown graphically in 

 figure 5= In 1922, 1923, 1925, and 1929, surumeika / Ommastrephes sloani 

 pacificus Steenstrup_7" were abundant, but no relationship was evident, 



f Relation to Low Pressures and Y/ind Directions 



(5) 



The writer has already plotted a curve of the tuna landings for 



each day at the Kushiro fish mai-ket- Designating the maximum catches 

 (big hauls) as A, the minimum (poor catches) as a, rising air pressure 

 as B, falling air pressure as b, and looking at their relations, we find 

 that in 1926 they were Abl2, AB7, aB12, and abl;, while in 1927 they 

 were Abl3, AB?, aB13, and ab6. In general it could be seen that the 

 big catches were made when the atmospheric pressure fell, and when the 

 pressure rose the fishing was poor^ 



Ihis means that when there is a low in the Japan Sea and the 

 direction of the winds blowing upon Hokkaido changes from northeast 

 to south and the weather becomes bad, then the fishing is good for 

 both long-line and drift-net fisheries, li?hen the low passes and 

 retreats to the Sea of Okhotsk or the Chishima area, the air pressure 

 rises, and the westerly winds blow on the area, the catch decreases. 



Furthermore with regard to the correlation between the progress 

 of lows and the tuna catch in the Kushiro region, taking as a starting 

 point the day on which the center of a low approached its closest to 

 Kushiro, when we thereafter look at the distribution of the number of 

 fish caught in each U-day pei'od before and after that time, we find 

 that the minimum catches are 3 days before and 1 day after and the 

 maxi.mum are U days and 1 day before and k days after the starting date , 



21 



