36o DISCOVERY REPORTS 



A study of the dispersal of whales involves two factors. First, the proportion of whales showing 

 dispersal and the range or distance to which these whales disperse. Second, the changes in this 

 proportion and range of dispersal over a period of time. 



The dates and positions of marking and of capture of the whales from which marks have been 

 recovered are known, and it is possible to construct time-charts which show diagrammatically the 

 dispersal of individual whales by means of lines connecting the position in degrees longitude of 

 marking in one whaling season, and the position of recovery in the same season or in a later one. The 

 lower end of each line is the longitude and date of marking, and the upper end of the line is the 

 longitude and date of recovery. The horizontal axis of the time-chart (Figs. 2, 3, 4 and 12) is divided 

 into degrees of longitude, the positions of the Areas II-IV being indicated. The vertical axis shows 

 the successive whaling seasons. The position in degrees of latitude is not used as this is to a large 

 extent dependent upon the date on which marking and capture took place. Recoveries and marking 

 made later in the whaling season are almost always in a more southerly position than the earlier ones 

 because of the southward movement of whales with the retreating ice during the course of the season. 

 The lines connecting the positions of marking and recovery may be termed ' tracks ', though they in 

 no way represent the actual movements of the whales in the period between these two events. 



In this method of plotting the data, vertical tracks indicate whales which have either remained in, 

 or more probably returned to, the longitude in which they were marked, although they may have 

 been captured some degrees north or south of the actual position of marking. Tracks at an angle to 

 the vertical indicate whales which have dispersed from the area of marking to a lesser or greater 

 degree. The time-charts also show the differences in behaviour of whales marked in the same area 

 during the same season and recovered in later seasons in widely separated areas, and the movements 

 of whales between Areas I-IV. 



The system of year-groups used by Rayner (1940) has been followed in this paper. Marks recovered 

 during the season of marking are referred to as the o-group, those recovered in the following season 

 after an average lapse of one year as the 1 -group, those after two years as the 2-group, and so on. 



It will be convenient to discuss dispersal in Fin and Blue whales separately. 



DISPERSAL IN FIN WHALES 

 At the close of the 195 1-2 season 218 marks had been returned from 208 Fin whales. For 201 of 

 these whales the position of capture is known. 92 returns have been made since Rayner's analysis. 

 Recoveries have been made in every one of the twenty whaling seasons from 1932-33 (when successful 

 marking was first carried out) to 1951-52, and they cover seventeen year-groups (Table 1). Details 

 of sex are recorded for seventy-five males and sixty-four females, and of length for 139 whales. 



Rayner (1940, p. 268 and PI. lix) gives details of an important mark (No. 3482) returned from a 

 Fin whale captured off Saldanha Bay, South Africa, about two and a half years after it had been marked 

 in the Antarctic almost directly south of the Cape of Good Hope. A second mark giving evidence of 

 Fin whale migration has now been obtained. Mark No. 9340 was fired into one of three Fin whales 

 on 11 October 1937, in the South Atlantic off the coast of Brazil, in position 28 03' S, 46 17' W. 

 It was logged when marked as a medium-sized whale, and was captured on 7 January 1949, after 

 a little over eleven years, in position 52 55' S, 38 42' W, off South Georgia, being recorded as 

 a male Fin whale 73 ft. long. This is the first evidence afforded by marking of the southward migration 

 of Fin whales from sub-tropical waters to the Antarctic. 



In view of the number of Fin whale recoveries with sex data, it has been thought worth while to 

 show the tracks of male and female whales separately on two time-charts, and on a third time-chart 

 the tracks of whales for which no record of sex is available. The two marks demonstrating migration 



