SUMMARY 295 



allowance must be made for the fact that catches are not fully representative samples of 

 the stock, and complete accuracy in the statistics cannot be expected. 



13. The whaling grounds of the southern hemisphere fall naturally into three 

 principal groups : tropical coastal waters in which Humpbacks are taken, subtropical or 

 temperate coastal waters with mixed catches, and the Antarctic where the industry 

 depends mainly on Blue and Fin whales. 



14. Humpbacks in the southern hemisphere are divided into several separate com- 

 munities or stocks between which there can be very little exchange. They are known to 

 frequent both the east and west coasts of each of the three southern continents in winter. 

 The positions of catches and the marking records of the ' William Scoresby ' show thai 

 in summer in the Antarctic they are segregated into clearly separate groups which, from 

 their position alone, might be expected to correspond with the separate tropical coastal 

 resorts in winter. Recoveries of whale marks clearly prove that an Antarctic group lying 

 south-west of Australia contains the same whales as appear off the West Australian coast 

 in winter, and a connexion has been established between a group south of South Africa 

 and the Humpbacks caught in winter off Madagascar. It is inferred that each of the 

 Antarctic summer groups has its own migration route to the coastal waters of a continent 

 lying in most cases approximately to the north of it. There appear to be five such groups, 

 but it is not certain that they are all rigidly separated from one another. Hjort, Lie and 

 Ruud divided the pelagic whaling grounds into four main areas on the basis of the 

 grouping of the whaling fleet. Each of these areas contains one of the Humpback 

 groups. 



15. The migrations and distribution of Blue and Fin whales are less clearly defined 

 than those of Humpbacks. Only one instance of migration between the Antarctic and 

 warmer waters has been demonstrated by whale marking, but there is abundant circum- 

 stantial evidence that such migrations take place. Little is known of their destination 

 when they move northwards in winter, but it is supposed that most of them become 

 dispersed in temperate waters. In the Antarctic Blue and Fin whales are more evenly 

 distributed than Humpbacks, but again the positions of capture and marking show that 

 they have at least a tendency (more definite in Blue than in Fin whales) to concentrate 

 in the same areas as Humpbacks. Whale marking has shown, furthermore, that they 

 generally return to the same part of the Antarctic after the northward migration, but 

 unlike the Humpbacks these species sometimes move from one area to another. 



16. Records of whales observed during voyages of the 'Discovery II' seem to con- 

 firm the Antarctic grouping of whales and suggest that the whole Antarctic zone might 

 be divided into six areas, each containing a community of whales. 



17. Observations by the ' Discovery II ', and the marking of whales by the ' William 

 Scoresby ', suggest that in the Southern Ocean the existing ratio of Blue, Fin and Hump- 

 back whales is of the order of 15, 75 and 10 % respectively. This estimate is not very 

 reliable, but it seems certain that Fin whales heavily outnumber the other two species. 

 The species ratio varies in the different Antarctic areas. 



18. The foetal records and the total catches in all localities indicate that in Blue, Fin, 



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