igg DISCOVERY REPORTS 



Elsewhere, Bigelow (1926) remarks on the vast quantities of euphausians, principally Thysanoessa 

 inermis, eaten by blue, fin, humpback and North Atlantic right whales off the New England coast, 

 referring particularly to CoUett's (1877) statement that 'sulphur-bottom stomachs frequently contain 

 300 to 400 liters of shrimps, and that occasionally one is taken with up to 1,200 liters of Thysanoessa '. 



Sizes and quantities eaten by baleen whales 

 Before we can begin to consider E. superba in its primary role as the diet of the Antarctic Balaeno- 

 pterids it is necessary first to get a clear idea of what size or sizes of this euphausian constitute the 

 actual feed and what, being too small, escape through the baleen plates and so do not contribute to 

 the diet. In the early days of the Discovery Committee's work at Grytviken, Mackintosh and Wheeler 

 (1929) examined the stomachs of 519 krill-eating whales, the majority of them blue and fin. 451 of 

 them, or 87%, contained E. superba and 68 were empty. The stomach contents were roughly classified 

 into large krill from 55 to 65 mm. long, medium krill from 40 to 50 mm. and small krill of 40 mm. and 

 less. As far as can be gathered from this rough classification the whales examined appear to have been 

 feeding for the most part on euphausians over 40 mm. long. It was noted, however, that in November 

 1926 there was a marked predominance in the stomachs of the smallest krill over the other classes 

 while from January to May 1927 there was a conspicuous mixing throughout of all three classes, the 

 smallest being particularly abundant. Some two years later Wheeler again visited Grytviken 

 where he measured to the nearest half centimetre a total of 39,081 E. superba from blue and fin whales 

 killed on the South Georgia grounds from October to April 1929-30. These hitherto unpublished 

 measurements, arranged in 10 mm. groups, are shown in Table 24. At first sight they give the 

 impression that blue and fin whales, those at any rate taken in the neighbourhood of South Georgia, 

 feed almost exclusively on euphausians over 30 mm. long, 88 % of the grand total measured being of 

 that order of size. The figures for December, however, show that occasionally at least, much smaller 

 krill of the 21-30 mm. group may constitute a by no means unimportant part of the diet, nearly 30 % of 

 the 1 2,037 measured in that month falling within this range. We get much the same general picture from 

 the observations of biologists and others who have worked in pelagic factories. Ruud (1932) for instance 

 gives details of the measurement of 1 785 stomach krill collected from whales taken by the floating factory 

 'Vikingen' from October to March 1929-30. According to his figures whale food over 30 mm. long 

 occurred commonly in the stomachs throughout the whole period the factory was operating, while in 

 October, November and December the 21-30 mm. group and under formed an important contribution 

 to the diet, occurring more frequently and in far greater abundance then than later in the season. 



From these records it would appear that the staple diet of the southern rorquals consists of euphau- 

 sians at least over 20 mm. long. A good deal of evidence, however, has recently come to light which 

 suggests that in spring and early summer, notably in October, November and December, great quanti- 

 ties of much smaller and younger krill may also be consumed. While exploring the possibility of using 

 whale meat on a large scale for human consumption on board the pelagic factory 'Terje Viken' in 

 December 1939, I examined on the 22nd of the month a fin whale killed in the eastern part of the 

 Weddell drift which had eaten, along with older krill, very large numbers of the last larval stage, the 

 Sixth Furcilia, together with early adolescents up to 20 mm. long. The stomach of this animal was 

 bulging with the meal it had eaten, the larval, adolescent and older krill being present in the 

 following proportions: 



