Table 13, --Fishing conditions by months (off the west 

 coast of Sumatra) 



In the composition of the catch, the yellowfin are overwhelmingly predominant, 

 amounting to 84 percent of the total for all tunas and spearfishes. Bigeye tuna are slightly less 

 than 9 percent sind spearfishes slightly more than 7 percent of the catch, these proportions rep- 

 resenting a conspicuous increase over the catch of the species in the Nicobar region. 



The seasonal changes in the catch rates for the various species are as shown in the 

 foregoing table. The bigeye catch rate reaches its peak in December and thereafter gradually 

 declines. Both the spearfishes and the yellowfin tuna show a tendency to a gradual increase with 

 the passage of time, at least up to the end of February. The sharks in general exhibit the same 

 trends of increase and decrease as the yellowfin and spearfishes, but in addition to the seasonal 

 changes they also appear to vary remarkably from one area to another, the catch rates appearing 

 to be larger close to shore. 



Damage to the catch by sharks appears on the whole to be proportional to the catch 

 rate of sharks, and on the days when large numbers of sharks were taken the damage from sharks 

 was also great. According to the reports of the Haruna Maru, the maximum shark damage was 

 actually 40 percent. This high rate was however rather exceptional and in general the damage 

 rate was about 10 percent. 



Considering the situation in the various parts of the cirea, it appears that whereas the 

 fishing conditions north of the Equator were comparatively stable, to the south of the Equator and 

 particularly in the waters off the Sunda Strait, which are at the southern limit of this area, the 

 fluctuations in the fishing conditions appear to have been extremely pronounced. 



The average weight of the fish in each day's yellowfin catch was reported. The data 

 indicate that the majority of the fish taken north of the Equator were centered around 35 kilograms. 

 A tendency can be detected for the fish to be somewhat smaller to the southward and larger to the 

 northward. An interesting phenomenon is seen in the fact that on days when the average weight 

 of fhe fish was around 35 kilograms, the catch rates were genercilly high whereas the catch rates 

 declined very greatly on days when the fish were much larger or smailler than this. According to 

 the reports of the Haruna Maru, very .small fish of 10 to 20 kilograms were taken on one or two 

 days at almost regular periods several days apart, and on these days the catch rates were very 

 low. The fishing stations were so close together that they can be quite properly regarded as a 

 single location. The significance of this sort of phenomenon cannot be adequately explained, but 

 it is thought to be worthy of attention both from the biological and the fishing points of view. 



The size of the yellowfin in the sea area south of the Equator appears to have been 

 completely different on either side of a boundary line in the vicinity of 6 S. latitude. The fish 

 from the north side of this line did not differ greatly in size from those taken in the vicinity of 

 the Equator, but those taken south of the line had an average weight of about 50 kilogranns. As 

 the season at which the data were collected was, of course, the sajne for this area and for the 



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