DISTRIBUTION AND MIGRATION 329 



Whale Research Group T.N.O. of Amsterdam has been studying this 

 problem for a number of years. With the assistance of Norwegian, 

 English and South African whalei's, scientists and institutions, the 

 Dutch team has been able to collect a wealth of data which has been 

 analysed by a number of biologists and mathematicians from the Amster- 

 dam Mathematical Institute. The findings so far have not been particu- 

 larly striking and the results have been mainly negative. However, from 

 them scientists have discovered what mistakes to avoid in the future 

 choice of specimens, representative body regions and measuring tech- 

 niques, and though it will take many years before we can hope to have 

 more positive information, it has already emerged that the thickness of the 

 blubber may vary from year to year, probably depending on the abun- 

 dance of food. Similar observations were made by E. Vangstein, the 

 Director of International Whaling Statistics in Sandjeford, when he 

 investigated the causes of the high yield in the 195 1-2 and 1953-4 

 seasons. (Measurements of blubber thickness may help to remedy short- 

 comings in processing techniques on certain factory ships, and C. E. Ash 

 has done a great deal of research on this subject.) 



Having discussed the distribution of whales in the Antarctic, we shall 

 now look more closely at their migratory habits. We have seen that krill 

 occurs mainly in a certain area surrounding the Antarctic continent and 

 in the Weddell Current. In the summer, these regions are only partly 

 covered with drifting ice, since, towards autumn, the impenetrable limit 

 of polar pack ice is near the mainland (see Fig. 177), except in the Weddell 

 Sea where it extends to about 63° S. In summer, therefore, the pack ice 

 does not keep the Avhales from their krill, but as the year goes on the 

 ice spreads farther north, and by November (the end of the winter), for 

 instance, it will have reached about 60° S. off Cape Horn or 55° S. south of 

 Cape Town. It therefore stretches almost as far as the Antarctic Con- 

 vergence, and cuts off all the normal krill concentrations from the whales, 

 the ovenvhelming majority of which then migrate to the north. 



While we knoAv that much, we know little about their final destination 

 or routes, though the answer to this cjuestion is important both scientifically 

 and also for practical reasons since, once we know the geographical origin 

 of whales caught by the various tropical and sub-tropical land stations, 

 we should be able to tell to what extent the population of a given Antarctic 

 zone is being reduced in and out of the Antarctic, and, if need be, we could 

 take protective steps. Moreover, if we knew that whales from a particular 

 zone return to it year after year, we could apply regional, rather than 

 total, sanctions. 



That whales migrate to the tropics and return to the Antarctic, though 



