THE SEI WHALE 



237 



Blue whales (Mackintosh and Wheeler, 1929), so that it appears that this species makes 

 an even poorer living in South African waters than do the latter. 



The average thickness of the blubber expressed as a percentage of the total length 

 is plotted by months, for male Sei whales in Fig. 66 and for females in Fig. 67. In 

 Fig. 66 immature and mature males are plotted separately, and in Fig. 67 immature, 

 mature pregnant, and mature but not pregnant females are plotted separately. The 

 length of 14 m. has been taken for separating immature from mature males and 14-5 m. 

 for females. The horizontal line in these figures is at the level of the mean blubber 



Feb Mar Apr June JuIl] Aug 



Fig. 66. Sei whale. Males. Mean blubber thickness by months. 



i^ ^ 05 -i 

 D -t- 

 C t30 

 ^ C 

 O _Q) 



H-^04- 



\- 

 1- o 



-Q q_ 

 J3 O 



,/ 



■ - ® I m m atu re 



Adult, resting' 



■-■© Adult, preg'ncint 

 O Adult, Idctating- 



o 



Feb Mar Apr Aug" Sep 



Fig. 67. Sei whale. Females. Mean blubber thickness by months. 



thickness for each sex as a whole. These figures show again the thinness of the South 

 African whales when compared with those from South Georgia, and also that immature 

 Sei whales of both sexes are constantly fatter than the mature males, and mature but 

 not pregnant females, in both localities. 



It must be remembered that Sei whales are only taken at South Georgia when there 

 is a scarcity of the larger and more profitable Fin and Blue whales ; that is, when there 

 is a scarcity of krill. Consequently, the curves of fatness do not show the increase 

 towards the end of the South Georgian season well marked in those for Fin and Blue 



