48 DISCOVERY REPORTS 



far away from the surface itself, and that it is only as Nauplii and Metanauplii, which in the strict 

 sense are not krill at all, that for a while (p. 97) it is strictly bathypelagic. Nor do we find these deep 

 early stages, as older larvae, coming to the surface at the Antarctic divergence any more regularly than 

 they do to the north or south of it. In fact it is rather the reverse (p. 310, Figs. 74 and 75, and especially 

 p. 354, Fig. 106). Hustedt (1958) reports on a collection of diatoms from krill stomachs south of 

 Kerguelen, adding many new records to Barkley's original list. In a brief account of the distribution 

 of the plankton in the Indian sector of Antarctica Korotkevitch (1958) again mentions £. superba, 

 noting it as one of the more typically occurring organisms of the plankton population of the waters 

 bordering the continental land. In a recent paper on the distribution of whales in the Atlantic sector 

 Arsenev (19580) states that with the approach of autumn and the formation of sea ice the krill descend 

 to depths inaccessible to the whales, rising to the surface again with the approach of spring. The same 

 appears in Kellogg and Whitmore (1957), who, in a reference to the immense swarms of E. superba 

 found in Antarctic waters, state that the migration of the whales towards the tropics coincides with 

 'the chilling of the surface water and descent of their favorite food '. It will be shown later, however 

 (p. 169), that there is nothing in our bathymetric data to suggest that such a migration takes 

 place. He makes some extremely interesting observations, however (Arsenev, 19586), on the distri- 

 bution of whales and their food, noting the ' high degree of regularity ' with which the biggest accumu- 

 lations of whales are found where the krill, as observed from the decks of vessels, is itself in great 

 abundance. He adds, of course, that this is not always the case, whales occasionally being encountered 

 in large numbers where no feed is visible, and vice versa, and suggests they may be congregating where 

 there is no apparent sustenance for them because their food is too deep to be seen. Nemoto and Nasu 

 (1958) and Nemoto (1959) are the first to show that in high southern latitudes the baleen whales do 

 not always feed exclusively on E. superba, Nemoto and Nasu, working on the Pacific side of Antarctica, 

 reporting Thysanoessa macrura as a major addition to the diet of fins and humpbacks, while Nemoto, 

 working in the same area, reports many of the sei whales there to be feeding on the swarming pelagic 

 amphipod, Parathemisto gaudichaudii} In the same paper Nemoto surveys the food and feeding habits 

 of the Antarctic and North Pacific baleen whales, showing what a striking difference there is between 

 the catholic diet of the northern species and that of their southern relatives. In these northern waters, 

 he records, the swarming Euphausia pacifica, Thysanoessa inermis, T. longipes, T. spinifera, T. raschii, 

 Calanus finmarchicus, C. cristatus, C. plumchrus and Metridia lucens, all contribute conspicuously to 

 the diet of one species or another, while fishes such as herring, anchovy, sardine, capelin, saury, 

 Alaska pollock, sand eel, mackerel, Atka mackerel, and the squid, Ommastrephes sloaneipacificus, in one 

 way or another are equally important as food. In view of the position in the Antarctic, where E. superba 

 alone is so widely eaten, it is indeed a remarkable list.^ And in so far as the north as a whole is con- 

 cerned it is far in fact from complete, for it omits a number of species Nemoto records as occasionally or 

 fortuitously swallowed and could of course be much extended if plankton and fishes from other boreal 

 regions were included. 



SCOPE OF THE OBSERVATIONS 

 In the fourteen years prior to the outbreak of the war the Royal Research Ships 'Discovery', 

 'Discovery II' and ' William Scoresby ', operating more or less continuously in far southern waters 

 from 1926 onwards, together accumulated a vast body of data on the Antarctic plankton as well as on 

 that of the warmer seas through which they passed on their passages to and from the whaling grounds. 



' Of even greater interest is the recent Japanese discovery of a small, evidently subspecifically distinct, race of 'Pigmy 

 Blue Whales' frequenting the warm West Wind region between Kerguelen and Heard Island (Ichihara, 1961). The small 

 krill on which these animals were reported feeding has been identified by Mr Nemoto as Euphausia vallentini. 



^ See also Sakiura, Ozaki and Fujino (1953), vvho give a shorter yet still distinctly cathoHc list. 



