364 DISCOVERY REPORTS 



as may be seen from the high proportion of empty stomachs. Even of those in which 

 food was present the vast majority are noted as containing only a few very small 

 Euphausiids. 



South Georgia, 1926-7 Season. Food appears to have been fairly plentiful during the 

 second part of November and first part of December, but to have fallen off a little in the 

 second part of December. It was fairly plentiful again during January and February, 

 but less abundant in March and April. The krill differed from that of other seasons in 

 the fact that there was in most cases a noticeable mixing of Euphausiids of different sizes. 

 These were not always mixed indiscriminately in the stomach. Large or small indi- 

 viduals might be found together in different parts of the mass of stomach contents, or 

 patches of large ones might occur in a mass of smaller forms, suggesting that the whale 

 had been feeding on separate shoals which differed in respect of the sizes of the 

 individuals. During this season there was a high proportion of unusually small 

 Euphausiids, though fully grown forms were also found from time to time. 



BLUBBER 



The highest grade of whale oil comes chiefly from the blubber, and the quantity and 

 quality of the blubber is therefore a matter of direct importance to the whaler. If 

 blubber were always of the same thickness and contained an invariable percentage of 

 oil, the size of the whale would be the determining factor in the total yield of oil from 

 the blubber. Other factors are present, however, which have an appreciable effect on 

 the yield, although the size of the whale must of course be the predominant factor. 



It is already known that differences of a regular nature occur in the thickness of the 

 blubber. Risting (1912), speaking of the Humpback, says that on the average it is 

 very fat in proportion to its size, and the blubber thickness varies according to the 

 season and food. In a later work (1928) the same author states that the quantity of oil 

 produced from a whale depends upon a number of factors, especially the size of the 

 animal, thickness of the blubber and the content of fat in the blubber and carcass. 

 Again, speaking of the stock of whales off the coast of South Africa, Risting mentions 

 the extreme fatness of pregnant whales — a fact which is noticeable at South Georgia 

 as well as at South Africa. Olsen (1914-15), reporting on the whales of South Africa, 

 notes that Fin whales caught from March to June were nearly all small and lean. The 

 fattest whales were females with foetuses. If accompanied by young the females were 

 leaner. 



Risting has used the total oil output of the whaling stations with the total number 

 of whales caught to give a figure for the "fatness" of each season's catch in barrels of 

 oil per "Blue whale unit." This unit is based upon the assumption that a Blue whale 

 gives twice as much oil as a Fin whale, two and a half times as much as a Humpback, 

 and six times as much as a Sei whale from the same field of operations. Calculated on 

 these lines the results show that whales in the south (South Georgia and South Shet- 

 lands) are far more productive than those occurring further north, say at Saldanha 

 Bay or Durban. 



