DISPERSAL IN FIN WHALES 369 



It seems curious that the 'corrected' histograms are generally less symmetrical than those for 

 ' actual ' numbers of marked whales killed. Perhaps where a few marked whales happen to have been 

 taken in a sector where the catches were small, the correction has given them undue prominence. 

 Nevertheless, more weight must be attached to the corrected than to the uncorrected diagrams. 



The following points may be noted : 



(a) The maximum range of dispersal is within 50 east or west (see pp. 367-8). 



(b) Among the ninety-nine whales in groups later than 2-group, only two (in the 3-4-5 group 

 series) have gone further than the 102 whales in the 0-1-2 group series, which seems to confirm 

 Rayner's conclusion that the range of dispersal in Fin whales is limited, and not necessarily in itself 

 progressive. 



(c) Although the range does not appear to increase, it is clear that the proportion of whales which 

 disperse from the immediate area of marking does increase as time goes on. If we say that whales 

 moving more than io° east or west have 'dispersed', then of the short-term recoveries (0-2 groups) 

 66% have not dispersed and 34% have done so, as compared with 40% and 60% respectively of the 

 long-term recoveries (3-17 groups). 



In Table 2 the same data are grouped in a different way. With the seventeen year-groups divided 

 into three series of six year-groups each, and the range of dispersal into units of 20 , one obtains 

 a fairly good numerical impression of the process of dispersal. It is seen that the percentage of whales 

 remaining in the marking area tends to decline while the percentage which have moved to between 

 io° and 30 east or west tends to increase. The series 6-1 1 group is perhaps anomalous in the high 

 percentage of recoveries made between io° and 30 west because 52-2% of the recoveries used were 

 made by catchers operating from South Georgia, as compared with 24-1 % and 18-9% in the series 

 0-5 groups and 12-17 groups respectively. 



Table 2. Corrected numbers and percentages of marked Fin whales which disperse east or zvest 



after various periods 



Marking 

 area 



West 50 



3o J 



3° 



o-5 

 groups 



6-1 1 

 groups 



12-17 

 groups 



37 

 3-4% 



o-6 

 47% 



o-6 

 2-8 c 



23-0 



21-0% 



4-2 



33-3% 



4"4 



20-4% 



63-9 



58-3% 



4-8 

 38-i% 



9-0 



4i'6% 



13-6 



12-4% 



27 

 21-4% 



6-2 



287% 



50 East 



Total 



5-4 



4-9% 



o-3 

 2-4% 



i-4 

 6-5% 



109-6 



12-6 



216 



This is perhaps as far as we can go with the available data. If larger numbers of whales could be 

 marked it may be that eventually some mathematical expression could be found to indicate approxi- 

 mately the rate of dispersal. It is doubtful, however, whether such an expression could ever be very 

 reliable, for dispersal may well be affected by other variable factors in addition to the intensity of 



whaling. 



Since there is a tendency for an increasing proportion of the marked whales to disperse as time 

 goes on, it might be expected that the distance to which they eventually disperse would also increase. 

 So far as the distance goes, however, it would seem that dispersal is. limited to about 50 east or west 

 after the first two or three years. This would be explained if for some reason dispersal normally 



