THE SEI WHALE 275 



which are immature and those which have just reached sexual maturity. There is no 

 older age group than the latter, and consequently few females that are more than just 

 sexually mature occur. These figures show unmistakably that few immature whales of 

 either sex take part in the southward migration, in which most of the Sei whales belong 

 to age groups older than that of whales which have just reached sexual maturity. 



ECONOMIC STATUS 



The Sei whale is not at present of any great economic importance on any of the 

 whaling grounds except Japan and Korea, and the west coast of Norway (Harmer 1928). 

 It was taken in some numbers in the seasons 1927-8 and 1928-9 by a whaling expedition 

 operating off the coast of Patagonia. This is due primarily to its small size (the oil yield 

 of six Sei whales is rated by Risting (1928) as equal to that of one Blue whale) and 

 further to the fact that in African waters it is usually in very poor condition. Conse- 

 quently, Sei whales are never taken when other, more profitable, species are available. 

 Nevertheless, the economic importance of the Sei whale is likely to increase greatly in 

 the near future, now that the stocks of the larger species are definitely dechning and 

 that the end of the commercial exploitation of the Blue whale, at least, appears to be in 

 sight. When the whaling industry seriously turns its attention to the Sei whale it is 

 to be expected that the species will very quickly be reduced to the same level of scarcity 

 as the larger species, because the hunting will be all the more intensive in order to 

 catch the large numbers necessary to produce the quantity of oil hitherto obtained. 



Figs. Ill, 112 and 113 show the numbers of Sei whales taken at South Georgia, 

 Cape Province and Natal for several successive seasons. The catches of Fin and Blue 

 whales taken are also given for comparison, and it is of interest to note that in every 

 season in which the figures show a peak for Sei whales it is correlated with a drop in 

 the curve for the larger species. These results are undoubtedly due to selective hunting 

 and demonstrate the caution with which figures of the commercial catch of Sei whales 

 must be accepted as showing the numbers of the species actually on the whaling grounds. 



The general stock of Sei whales is doubtless at present little disturbed by commercial 

 whaling and is in a state comparable with that of the stocks of the larger whales before 

 the exploitation of the southern whaling fields. A great decline in numbers may be 

 expected if the species is taken in large quantity. The decline will be all the more 

 rapid if the species is captured in numbers off the coasts of South Africa, where the 

 whales are taken while on their breeding migration. In this area there are large numbers 

 of immature whales, and their poor condition will lead to the capture of excessive 

 numbers in order to make up the desired quantities of oil. 



Since this report was written the International Whaling Convention has, however, 

 put forward proposals for the further protection of this species, together with other 

 whales. 



