DISPERSAL IN FIN WHALES 365 



contrast between the tracks of males and those of females : very few of the females marked in the 

 South Georgia-Shag Rocks area (35-42 W) have dispersed eastwards, whereas a number of males 

 have done so. The bunched tracks in about 40 W in Fig. 3 seem to represent a local community 

 of whales in which the females have kept closely to their own territory for many years. 



Fig. 4 shows the tracks of sixty-two Fin whales of unknown sex. In Area III there is an interesting 

 group of three whales marked and recovered in the same seasons, and showing almost no dispersal 

 after fourteen years. 



These time-charts (Figs. 2, 3 and 4) are intended to give an overall view of the east and west 

 movements of Fin whales, and it is worth while, as a further step, to see whether the frequency, 

 rate, and range of dispersal can be more definitely indicated. 



Although the time-charts show that most but not all Fin whales are taken near the longitude of 

 marking, they do not give a reliable indication of the proportion of whales which disperse to other 

 longitudes, because the chances of marks being recovered in one sector or another must obviously 

 be affected by the total number of whales killed in the various sectors. For example, if a number of 

 marked whales had dispersed to longitudes where little or no whaling took place, none of them 

 might be recovered and we should have no knowledge of their dispersal; or if a smaller number 

 moved to a region of intense catching several might be recovered and the indication of dispersal 

 would be positively biased. The distribution of the catches does in fact vary considerably (see 

 Figs. 5 and 6), and it is clearly necessary to apply a correction accordingly to the data from recovered 

 marks. 



The papers in Hvalradets Skrifter mentioned above give, for the seasons 1932-33 to 1936-37, 

 tables showing the number of whales caught by pelagic factory ships in 'squares' measuring io° of 

 longitude by io° of latitude south of 50 S, and from these it is easy to obtain the whole catch in each 

 sector of io° of longitude south of 50 S, which is all that is needed for the present purpose. 1 The 

 Bureau of International Whaling Statistics have kindly supplied similar tables for the seasons 1937-38, 

 1938-39, and 1945-46 to 1951-52. The catches at South Georgia must also be taken into account. 

 These are given for all years in the Bureau's published International Whaling Statistics, and we have 

 certain unpublished data from which it can be estimated that in the period 1932-37, 96% of Fin 

 whales and 99-85% of Blue whales were taken in the sector 30-40 W and the remainder (4% and 

 0-15%) in 40-50 W. It has been assumed that these ratios obtain for each season from 1931-32 to 

 1951-52 inclusive. There remain the pelagic catches in the war-years, and detailed statistics for these 

 are not available. Some British, Norwegian and Japanese factories were operating in 1939-40 and 

 1940-41, and some marks were recovered in these seasons, but pelagic whaling ceased after 1940-41 

 until 1945-46, except for one factory which operated in 1943-44 and 1944-45. The International 

 Whaling Statistics, No. xxvi, 195 1 (p. 23) gives the catch for some of the factories in Areas II-V for 

 1939-40 and 1940-41, and No. XVII, 1947, gives the total numbers of factories operating in these 

 seasons. From these figures one can calculate a hypothetical distribution of the .catch in io° sectors 

 if one assumes that it was distributed in these sectors in the same ratio as in the two preceding 

 seasons, 1937-38 and 1938-39. This assumption is not very reliable, but it is probably nearer to the 

 truth than to assume that the catch was evenly distributed over all sectors (i.e. to make no allowance 

 for the distribution of the catchers). A similar calculation has been made for the one factory which 

 worked in 1943-44 and 1944-45, and thus we have actual or hypothetical sector totals for all the 

 Fin and Blue whale catches from 1932-33 to 1951-52. These are shown diagrammatical ly in Figs. 5 

 and 6. 



1 These tables give rather less than the total Antarctic pelagic catch, but are sufficient to show approximately the distri- 

 bution of the intensity of catching. 



