266 DISCOVERY REPORTS 



In area I there is clearly a higher percentage of Humpbacks than in area II, but the 

 percentage in Tables 19 and 20 differ so widely that no reliance can be placed on them. 



In area III the figures in Tables 19 and 20 agree very closely in respect of the Blue/Fin 

 ratio. The percentages of Humpbacks do not tally very well, but for reasons given above 

 the 'William Scoresby's' ratio of 5-8 % is much more likely to be correct than the 

 ' observed ' 2-7 %. In any case we know that Humpbacks are plentiful in at least a part 

 of area III. In this area, then, there is reason to believe that the ratio of Blue, Fin and 

 Humpback whales is of the order of 18, 76 and 6 % respectively. 



For reasons given above the data for areas IV-VI are largely unreliable, though it 

 would seem that there are rather more Blue and Humpback whales in IV than in III. 

 Here the catch statistics (p. 264) are helpful, for in area IV they show larger catches of 

 Blues and Humpbacks, and fewer catches of Fins than in area III. 



The catch statistics for area V are not properly comparable with the other areas, for 

 they cover only the two seasons 1929-31. At that time fewer Blue and more Fin and 

 Humpback whales were taken in area V than in areas III and IV, but, on the other hand, 

 very few whales have been taken there since 193 1, and the local stock of Blue whales may 

 not have been reduced so much in recent years as it has in areas II-IV. 



In area VI no Humpbacks were identified during the voyages of the ' Discovery II ' 

 and this is to be expected, for it is far from any coastal waters to which this species might 

 be expected to resort on its northward migration. As to the Blue/Fin ratio in area VI 

 it can be said that the figures in Table 20 so far as they go suggest a higher proportion 

 of Fin whales than in most other areas. 



In Tables 17 and 18 (pp. 262-3) the total ratios by observation and marking suggested 

 that there were about 13-14 % Blue, 76-79 % Fin and 7-1 1 % Humpbacks. It was 

 mentioned that area II was unduly represented in these figures, and it is now evident 

 that in that area the proportion of Fin whales is higher, and of Blue and Humpbacks 

 lower, than the average for all areas. I should suggest that in the Southern Ocean as a 

 whole, in, say, the year or two preceding 1939, the total population of Blue, Fin and 

 Humpback whales might include 10-20 % Blue, 65-85 % Fin and 5-15 % Humpbacks. 

 This is a tentative estimate, but it seems certain at least that the stock of Fin whales out- 

 numbers the stock of Blue whales several times over. 



SEX RATIO 



There is no established means of distinguishing the sex of a whale in the water, 

 except, for example, when a female is obviously accompanied by its calf. Consequently 

 estimations of the sex ratio can be based only on statistics of catches and the ratio in 

 foetuses. It is very difficult to say whether there are actually more of one sex than of the 

 other, for there is clearly no great disparity, and an apparent preponderance of one sex 

 might simply be the result of some degree of segregation. The foetal sex ratio should 

 represent the relative numbers of each sex born, but it is not necessarily to be assumed 

 that the two sexes survive in the same ratio to maturity. 



