MIGRATIONS AND DISTRIBUTION 25! 



relative abundance of whales in different regions, has added a new complication. How- 

 ever, Rayner (1940) has shown that like Humpbacks they tend as a general rule to return 

 to the same Antarctic locality after their winter migration to warmer waters, and that 

 their movements from one Antarctic locality to another are to some extent restricted. 

 This is perhaps the most important fact which has emerged from whale marking, for it 

 is the key to the whole problem of whale distribution. It implies, among other things, 

 that although Blue and Fin whales are distributed more or less continuously around 

 the Antarctic continent there is no indiscriminate shuffling of the stocks, either in the 

 Antarctic or in warmer waters ; and a reduction of the stock, for instance as a result 

 of whaling, is to be regarded, at least temporarily, as a local reduction rather than 

 a subtraction from the general pool of whales in the Southern Ocean. 



Although Blue and Fin whales in the Antarctic are not separated into clearly isolated 

 communities, the movements of factory ships suggest a grouping which is not unlike the 

 grouping of Humpbacks. These movements of the whaling fleet, and the positions and 

 numbers in which whales of each species are caught, naturally constitute one of the most 

 fruitful sources of evidence on the actual distribution of whales. Reference has already 

 been made to the four major whaling grounds distinguished by Hjort, Lie and Ruud, and 

 it has been shown above that in each of these areas there is a distinct community of 

 Humpback whales, each of which is related to a corresponding coastal region in lower 

 latitudes. The areas II-V (see Fig. 2) were not, however, defined on the basis of Hump- 

 back catches, but on the grouping of the whaling fleet as a whole which must be in- 

 fluenced primarily by the distribution of Blue and Fin whales, especially the former. 



Hjort, Lie and Ruud have shown that there is a remarkable similarity in each suc- 

 cessive season in the distribution of the factory ships which applies not only to their 

 concentration in separate groups in each of the areas, but also to movements during the 

 season. In the third of their series of articles (1933, p. n) they point out that these 

 things are not a matter of chance, but are due to a regularity in the migrations of whales 

 which is connected with the hydrological conditions, and they postulate more or less 

 self-contained current systems, at least in areas II, III and IV. In the same article (p. 12) 

 they say : ' . . . the remarkable agreement we have found in the November charts for the 

 last two seasons suggests that there is a regularity in the distribution of the grounds 

 which extends even to details.' Some variation of course arises from season to season 

 as a result for instance of exceptional ice conditions, and the relative intensity of whaling 

 in the different areas is affected perhaps by the decline in the stock of Blue whales. This, 

 however, does not affect the general conclusion that since the factory ships become more 

 or less segregated on four distinct whaling grounds (in areas II-V) it is to be supposed 

 that there is a tendency for stocks of Blue and Fin whales to become segregated into 

 corresponding groups. 



For a better assessment of this tendency to segregation the statistics of catches and 

 the data from the ' William Scoresby ' have been treated in the same way as for Hump- 

 backs. The total catches of Blue and Fin whales, and the 'whales per day', are given in 

 Table 11 for two seasons, but for these two species more than two seasons' data are 



