THE STOCK OF WHALES 463 



Bay the fat adult whales which are presumed to have recently arrived from the southerly 

 feeding grounds, are not taken only at the beginning but well on into the middle of the 

 season. It is true that those taken there in the latter part of the season are not so fat 

 as those which appear earlier and it may be that some of them have started again on the 

 southern migration, but the fact remains that the condition of the majority of these 

 mature whales suggests that they had been recently feeding, and not on the scanty krill 

 of the South African coast. 



There are two possible explanations of this state of affairs. It may be that the 

 "north-south" migration lags behind the season so that instead of a punctual southerly 

 migration in spring and northerly migration in autumn there is a continuous move- 

 ment to the south through most of the summer and towards the equator through most 

 of the winter. Or it may be that a kind of "one-way" system operates, according to 

 which some sort of procession passes through the South Georgia area. In this case the 

 whales which appear early in the whaling season at South Georgia would be on their 

 way back towards the equator by some other route during the second half of the season 

 and so on. The point, however, cannot be regarded as settled at present. Possibly both 

 factors operate to some extent. There is, however, some indication of a return of some 

 of the whales at the end of the South Georgia season. There was, for instance, a slight 

 increase in the number of adult male and pregnant female Fin whales in May 1925. 

 The adults of both sexes also showed a relative increase again in April 1927 (see tables 

 on pp. 456 and 457). Among Blue whales also there was an indication of a return of 

 sexually mature whales at the end of the 1924-5 season. 



CONCLUSIONS REGARDING THE WHOLE STOCK 



The conclusions, which have a direct effect on our knowledge of the stock, may be 

 summarized as follows: 



1. Although it has not yet been possible to make a proper comparison between the 

 whales of the northern and southern hemispheres, records of the external characters 

 and bodily proportions have shown that a very complete resemblance exists between 

 the Blue and Fin whales of South Georgia and South Africa and they have revealed 

 no definite grounds for separating any of these whales as distinct sub-species or races. 

 The general similarity of all the whales examined suggests that it is possible for 

 interchange to take place between the whales of different localities and for a reduced 

 number of whales in one locality to be replenished from the population of another. 

 In a sense this is a negative result, but it is important. 



2. Among Blue and Fin whales it is a general rule that the two sexes are everywhere 

 mixed together in roughly equal numbers, though at times a certain amount of segrega- 

 tion may take place. Presumably less harm is done to the stock by the killing of a male 

 than of a female and it is therefore of some importance to know that of a given number 

 of whales killed approximately only half will be females. 



