(5) The first drift-net catches off Erimosaki are made at water tempera- 

 tures of about lli°C, Ihis figure is higher in warm years and lower in 

 cold years. During the main season off Kushiro the water temperatures 

 are 1U«0°C to 18„0 C At the close of the season there is good fishing 

 even at temperatures of around 10„0°Co After visiting the coastal waters 

 of Hokkaido the fish are accustomed to cold water and their resistance 



to water ten^jerature is greato 



(6) The tuna like to live in zones of mixed water « 



(7) In the Pacific coastal -waters of Hokkaido there are three streams of 

 the Chishima cold current. The warm currents are three streams of water 

 from the Kuroshio system and the Tsugaru warm current, 



(8) The temperature differential between the surface and the 50-meter 

 level in transverse observations 10 to 50 miles south of Kusniro and 

 the average catch per boat per cruise are inversely correlated, with a 

 correlation coefficient of r - -Oo^lo 



(9) The position and strength of the ocean currents control the tuna 

 fishery. When the coastal stream of the Chishima cold current and its 

 second stream do not separate, or the third branch of the warm current 

 does not break through the cold current off Kushiro, the fishing is 

 good at Kushiro and poor at Etorofu Island, When the third branch of 

 the warm current does not flow off Erimosaki j the fishing is poor at 

 Kushiro and good at Urakawa, 



(10) The fishing is sometimes good when the v»arm currents are flour- 

 ishing, and in most years the fishing is good in the latter part of 

 July. 



Cll) The tuna-fishing situation in the southern waters of Japan and 

 that of the Hokkaido waters appear to be directly opposite » There also 

 seems to be some correlation with the number of sunspots, but this is 

 hard to affirm because of the paucity of data, 



(12) Fishing is poor in years when broadbill swordfish, skipjack, 

 albacore, and other warm-water fish migrate into the area. 



(13) Generally when a low is approaching and the wind direction becomes 

 easterly the fishing is good, 



(lii) There is a correlation between lunar age and the drift-net fishery. 

 In general the fishing is good from the third to the eleventh day of 

 the lunar month. 



26 



