RELATIVE ABUNDANCE OF SPECIES 



263 



by whales marked, especially in the Blue/Fin ratio which works out at 1 to 5-7 by 

 observation and 1 to 5-9 by marking. It should be noted, however, that a larger number 

 of observed whales have been identified in the Falkland Islands sector (i.e. in area II, 

 see Table 20, p. 264) than in other parts of the Antarctic, and although most of the 

 'William Scoresby's' marking has been on the eastern grounds, the South Georgia 

 figures give a similar bias to the total marking ratio. The differences between the 

 marking ratios for the ' William Scoresby ' and for South Georgia are clearly due to the 

 fact that South Georgia is in area II while the 'William Scoresby' worked for three 

 seasons in areas III and IV and only one in area II. This, of course, explains the big 

 discrepancy in the Humpback ratio, since this species is so scarce in area II. 



Table 18. Species ratio by numbers marked 



The Blue/Fin ratio, which indicates such a heavy preponderance of Fin whales, is of 

 much importance, but consideration must be given to a possible source of error in so 

 far as the ratio is calculated from observations at sea. As mentioned above, it has not 

 been the practice for the ' Discovery II ' to alter course to get a nearer view of the whales 

 seen at a distance. If, then, it were found that Fin whales exhibited more curiosity than 

 Blue whales, and had a habit (in the manner of dolphins) of deliberately approaching a 

 ship, the number of Fin whales identified would be unduly high in comparison with 

 Blue whales. But, on the other hand, if this were so we should expect a lower proportion 

 of Fin whales in the ' William Scoresby's' data, for that ship endeavours to pursue whales 

 until they are within close range. If there is therefore any such difference in the habits 

 of Blue and Fin whales it does not seem sufficient to account for the estimated pre- 

 ponderance of Fin over Blue whales. It can be seen from Figs. 3, 5, 6, and 7 that the 

 species ratio varies in different parts of the Antarctic, and the existence of such variations 

 has been made clear enough by Hjort, Lie and Ruud. They point out (1934, p. 19) that 

 the catch statistics do not provide a reliable means of estimating the proportions of Blue 

 and Fin whales in the sea. Their figures, however, do give an indication of how those 

 proportions vary in the different areas. Bergersen, Lie and Ruud (1939, p. 18) give a 

 table showing the different species as a percentage of the total catch in each season since 

 1929-30. During these years the proportions have altered considerably, Blue whales 

 decreasing heavily and Fin whales increasing. In almost every year, however, the per- 

 centage of Blue whales has been higher in areas III and IV than in area II, and the same 



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