J44 DISCOVERY REPORTS 



necessarily, however, in the same year) by our stramin nets, the stomach length frequencies being 

 based on the 'Vikingen' and 'Hektoria' measurements of Ruudand Crimp. Although a high propor- 

 tion of them come from the Weddell stream, net and stomach samples are not necessarily from identical 

 regions, but for purposes of this rough comparison it is the approximate date that matters. It will 

 be seen that as the season advances the whales tend to sample the krill in much the same way as our 

 nets do, from October to March the young and old broods being represented in the same stomach 

 with much the same frequency as they are encountered at the same time in the plankton. There is 

 a distinct tendency, however, and perhaps a natural one, for the whales to be the more efficient 

 samplers of the older krill, a tendency doubtless associated with the measure of avoidance the larger, 

 and particularly the very large, euphausians undoubtedly (p. 262) take of our nets. Einarsson (1945) 

 also remarks on this tendency in a reference to the various animals, notably whales, that ' are more 

 mobile in their pursuit of the Euphausiids than our nets are'. At the same time it is clear that the 

 spacing of the baleen plates puts a limit to their sampling of the young 10-12 month old broods 

 encountered from October to December. Here it is the nets that are the more efficient samplers, the 

 tendency being for the whales to sample such broods principally in the upper reaches of their length 

 range. And so it may be supposed that while the adult krill suffer heavily through the depredations 

 of their immense predators the young yearling swarms survive in at least some measure of immunity 

 to contribute to the mass of the available feeding-stuff later in the season. 



Although some slight information is available from the north we know very little about the quantities 

 of food consumed by the large southern rorquals, and as Thorson (1958) has said of predators 

 in general facts about this are urgently needed. All we can be certain of is that depredation must 

 occur on a stupendous scale. Bennett (1931) remarks, 'The amount consumed daily must be 

 enormous, for whales taken in areas where "whale food" is plentiful have the stomach so distended 

 as to be on the point of bursting when that organ is removed from the body. In the case of large 

 whales, the stomach contents consist of many cart-loads'. Perhaps one cartload, however, or at 

 most two (PI. Ill), would be nearer the truth. Upwards of two cartloads are clearly indicated in an 

 impressive photograph by H. W. Symons^ published by Slijper (1958, Fig. 167), and in an equally 

 striking illustration by Hjort and Ruud (1929) a bulging fin-whale stomach might it seems be carrying 

 a similar quantity. Hardy (1959) gives much the same broad volumetric estimate, remarking that it 

 is 'very impressive, when a whale-stomach is cut open on the flensing platform, to see a cartload or 

 so of these little shrimps come gushing out'. I think, however, that Budker (1957) may be going too 

 far when he suggests the possibility that a large baleen whale could swallow a ton of krill at a single 

 mouthful. Hjort (1933) probably comes closer to the truth when he says 'they take a huge mouthful, 

 say several barrels full '. 



Guldberg (1887), citing Collett (1877) on the quantities of Thysanopoda inermis (= Thysanoessa 

 inermis) eaten by blue whales in northern waters, states that ' Collett fand gewohnlich 2-3 Tonnen 

 (3-400 Liter) im Magen; aber die sehr grossen Individuen, wenn sie sich richtig voU gefressen 

 hatten, batten bis 10 Tonnen'. Here, clearly, Guldberg is using 'Tonne' in its German meaning of 

 tun, cask or barrel, and not, as it also means in German, as the metric ton or 1000 kg. Assuming his 

 euphausians to have been adult T. inermis, which grows to about 30 mm., and that a litre of these 

 would weigh about 2 lb. ,2 Guldberg's 300-400 litres would work out at between 6 and 8 cwt. 

 and his 10 Tonnen (= say 1300 litres) at approximately i| English tons. If, however, his Tonne 



1 An equally remarkable photograph by Professor Johan T. Ruud, showing what seems might be at least two cartloads 

 (perhaps 2 tons), appears in Clarke's (1954) Elements of Ecology. It is said to be of the opened stomach of a southern right. 



2 A litre of E. superba in the 21-30 mm. range, drained of its fixative through muslin so as to simulate the packed and damp 

 condition in which it would come from a whale's stomach, does in fact weigh 2 lb. 



