262 



DISCOVERY REPORTS 



The best data again are forthcoming from the third, fourth, and fifth commissions 

 of the ' Discovery II '. On the fifth commission especially specific identifications were 

 much surer, for by then there were more persons on board who had had experience of 

 whale marking and of work at whaling stations. Mistakes are so easily made that many 

 doubtful identifications must be eliminated as too uncertain to be of any value. The dis- 

 tinction in Table 17 between 'certain' and 'probable' identifications is inevitably to 

 some extent a matter of opinion, but in drawing up the table I have put in the first 

 category only those records which were noted as certainties by observers who had had 

 experience of whale marking or work at whaling stations and had thus seen large numbers 

 of whales at close quarters. In the second category are included records noted by the 

 same observers as 'probable' and some observations by other persons either at very 

 close range or confirmed by more than one observer. Identifications by less practised 

 observers are disregarded. The figures are thus curtailed but should be reliable, and I 

 believe that Table 17 is a fair statement of the proportions in which the species were 

 actually seen, except that the ratio of Humpbacks might be a little too low, for it is 

 sometimes difficult to be certain of a Humpback at ranges at which the dorsal fin of a 

 Blue or Fin whale can be distinguished. 



Table 17. Species ratio by observations at sea 



The most important figures shown in this table are the percentages of the certain or 

 almost certain identifications, and it will be seen that 13-9 % were Blue, 79-5 % Fin 

 and 6-6 % Humpback. The 'probable' identifications give a higher percentage of Blue 

 whales, and it is a curious fact that the more doubtful identifications are admitted the 

 higher becomes the proportion of Blue whales. 



These observations have been distributed very widely in the Southern Ocean, but the 

 quantity of data is admittedly small and is not very evenly distributed in the different 

 areas, so that the ratio needs checking from other sources of information. For this 

 purpose we have an instructive body of data in the records of whales which have been 

 marked or shot at. 



Taking first the whales actually marked, Rayner (1940, p. 252) gives a table showing 

 the numbers of whales marked by the ' William Scoresby ' operating on the oceanic 

 whaling grounds of the Antarctic, by hired whale catchers around South Georgia, and 

 by the 'Discovery II'. The proportions are shown in Table 18. 



There is here a very striking similarity between the species ratio by observation and 



