DISPERSAL IN BLUE AND FIN WHALES 



By S. G. Brown 



(National Institute of Oceanography) 

 (Text-figs, i -i 4) 



INTRODUCTION 



IN an investigation of a population of almost any mobile animal a matter of obvious importance is the 

 range of movement of the individuals within the area which the whole population inhabits, and this is 

 also of practical significance when the animals are economically valuable. In the southern summer 

 baleen whales are distributed over several million square miles in the Southern Ocean, and in the 

 winter they generally migrate into warmer waters. One of the many objects of marking whales is to 

 gain information on the time, direction and range of these seasonal migrations, which tend to run in 

 a north and south direction ; but it is also necessary to examine movements in other directions, and 

 to consider whether different parts of the Antarctic may be inhabited by the same whales year after 

 year, whether there are segregated communities of whales, or whether there is much or little inter- 

 change of individuals by lateral dispersal. 



In a programme of whale-marking under the Discovery Committee, over 5000 whales were marked 

 in the Antarctic between 1932 and 1939. By the end of the latter year 203 marks had been returned 

 from 187 whales, and at this stage an analysis of the results was published by Rayner (1940). His 

 report gave particulars of the method of marking and a statement of the data available. He plotted all 

 the positions of marking and recovery on a series of charts, demonstrated some of the migration routes 

 of Humpbacks, and pointed out among other things that Blue, Fin and Humpback whales generally 

 returned year after year to the same part of the Antarctic as that in which they were marked. He 

 emphasized, however, that there were exceptions to this tendency among Blue and Fin whales, some 

 of which were found to have moved for varying distances to the east or west, either within a few 

 weeks or months, or after one or more years. Although full details of these movements were shown 

 on his charts he did not at that stage make a quantitative analysis of them. 



Hardly any marking has been done in the Antarctic since 1939. In 1950 some whales were marked 

 in South African waters, but these were mainly Sperm whales. However, since Rayner's report was 

 written a further 104 of the pre-war marks have been recovered in the Antarctic from twelve Blue 

 and ninety Fin whales. Two more have been recovered from Humpbacks in Australian waters. This 

 new material does not add much to the statistical value of the data available to Rayner, and a full 

 analysis is probably best postponed until more marks have been recovered. However, these later 

 recoveries extend over a much longer period than those previously described — up to thirteen years 

 from Blue and seventeen years from Fin whales. It is useful therefore to list the total recoveries 

 to date, and to see what new information can be extracted. The present paper can be regarded as 

 an interim report, mainly concerned with dispersal in time, which is examined on a quantitative 

 basis. 



A full list of marks returned from Blue and Fin whales, with sex and length when available, is 

 given in the Appendix, Tables 6 and 7, pp. 378-84. 



This work was undertaken at the suggestion of Dr N. A. Mackintosh who has given me some 

 general guidance on the treatment of the subject. I have also to thank Mr J. Crease, of the National 



