In short, the water temperatures of the lOO-'.iiei&er j.ayers in each ocean 

 current recently showed similar drops. The drop was most noticeable in the 

 equatorial countereurrent area, followed by the northern equatorial current 

 area and the southern equatorial current area in that ordero On the whole, 

 there was a great change as compared to a normal yearo 



When the meaning of this change is considered in connection with fish- 

 ing conditions, two points must be considered? the drop in surface water 

 temperatures to 27-28 degrees in the coastal and high sea areas, and the 

 drop in the water temperature of the 100-meter layer to below 20 degrees in 

 the equatorial countereurrent area„ (Yellowfin tuna, which are the largest 

 element in the tuna catch, are more abundant in the equatorial counter- 

 current area than in the northern equatorial current area. Details concern- 

 ing fishing conditions in the southern equatorial current are not as yet 

 known. ) 



Next we studied fishing conditions in the coastal waters of the Palau 

 group and sought their relationship with sea conditions. We first gathered 

 the recent data on hand concerning skipjack fishing. The figures on the 

 skipjack catch for January were set up and a comparisor was made. 



The exceptionally small catch for this year may be partly due, 

 naturally, to the lack of live bait, but the major cause may be attributed 

 to the fact that the water temperature dropped below 28 degrees. According 

 to data from past investigations (see this Station's Oceanographic Survey 

 Report Number 1), skipjack are not taken at water temperatures of 27-28 

 degree So 



* 1 KaS - 3.27 pounds 



As previously explained, the eastern shores of the Palau group were 

 washed by the main current of the northern equatorial current during January 

 and February of this year and this type of ocean current was also seen in 

 January and February of 194-0, The good catch of skipjack during January and 

 February of 194-0 was explained by the belief that "abundant skipjack are 

 found in the northern equatorial current". From the fishing conditions of 

 this year, however, we learned that even though the chores are washed by the 

 main stream of the equatorial current, skipjack cannot be found when the 

 water temperature falls to 27-28 degrees (water temperatures in 1940 were 

 over 28 degrees). 



In regard to tuna fishing, the Zuiho Maru conducted operations at five 

 stations in the equatorial countereurrent area during its two voyages at 



