more numerous in the season of northerly winds with slightly snnaller ones predominating during 

 the season of southerly winds. The average weight for the whole year is about 44 kilograms, 

 rather markedly smaller than the fish of the Flores Sea region and considerably larger than,^those 

 from the equatorial Pacific. It is an interesting fact that if we compare the condition factor— 

 for yellowfin taken at the height of the season of northerly winds, those from the Celebes Sea giy/e 

 markedly lower values than those from the East Philippine Sea Eind the Sulu Sea (see Nakamura— ). 



The Shonan Maru carried on its investigations using a special kind of fishing gear with 

 a float attached to each branch line. The object of using this sort of gear was to determine accu- 

 rately the fishing level (or swimming level) for the tunas and spearfishea. With the gear common- 

 ly used it is not easy to determine the depth at which the hooks are hanging, but with the Shonan 

 Maru's gear the position of the hook could not be deeper than "length of branch line plus length 

 of float line, " so that the limit at one extreme was always given. 



Looking at the results of investigations made with this sort of gear, we see that 

 there are rather conspicuous differences in catch rates between branch lines. In one remarkable 

 example the total length of the float line and branch line was 160 meters and a considerable catch 

 was made, the catch rate being 6.0. In general the catch rates were highest where the total 

 length of float line and branch line was about 100 meters, but rather high catch rates were also 

 obtained where the total length, was about 50 meters, which appears to indicate that there are two 

 fishing levels (see Nakamura— ). 



It is considered that the reason for the existence of two fishing levels is that the 

 catch of spearfishes in this sea area is fairly great and that the spearfish catch rates show high 

 values at about the 50-meter level while the yellowfin are taken in the greatest numbers at about 

 the 100-meter level. The following table shows one example. 



Table 22. --Fishing conditions at different depths 

 (Celebes Sea, July-August 1934, 

 Shon^ln Maru) 



Note: (1) Depths are length of branch line plus length 

 of float line. 



As was noted earlier, it appears that fishing conditions in this sea area vary 

 markedly with the season. The local variations in the fishing conditions are not well understood, 

 but it appears that they also exist. If the season and the locality are suitably taken into account 



W 

 5/ Condition factor is -^ x 1000; L = body length, W = weight. 

 L^ 



6/ Nakamura, Hiroshi . Tuna Fishery Resources and Fishing Grounds, Fisheries Quarterly, II, 

 ~ December 1949. 



]_/ Nakamura, Hiroshi. The Tunas and Their Fishery, Takeuchi Shobo, 1949. 



57 



