PHYSICAL ENVIRONMENT 7, 



that is to say in such parts of it as are covered every winter, must be just as scarce as it has been shown 

 to be (compare again Figs. 5 a and 5 h) when the whole of this area lies open to the south. On equally 

 good grounds we may assume that temporary ice-fields in richly populated regions such as the 

 Weddell and East Wind drifts must mask, at the right season of the year, populations of larvae, 

 adolescents or adults no less rich than those that are known to exist in both great currents when they 

 are not so encumbered with ice. 



Racovitza (i900^») of the 'Belgica', the only vessel that has ever wintered at sea in the pack of the 

 East Wind drift, refers to the immense shoals of Euphausia that exist there below the winter ice, while 

 Wilton (1908) records that Euphausia were commonly seen and captured in large numbers at the 

 surface through holes cut in the sea ice near the ' Scotia's ' wintering station at Laurie Island. 



An isolated but highly interesting observation on the occurrence of krill below the winter ice of 

 high East Wind lattitudes has just been published by Fuchs (1958). It was obtained while the 

 Commonwealth Trans-Antarctic Expedition was wintering at Shackleton Base in Vahsel Bay when 

 in May 1957 a large fish trap was being used through a hole cut in the ice over a depth of 500 fathoms. 

 He writes : 



The hole through which the trap had been let down was frozen over and when we broke through, countless clusters 

 of ice crystals an inch or more in diameter floated to the surface. At last a patch of clear water was obtained and 

 we could see by the light of our torches numerous pink shrimp-like animals. These were Euphausia or 'krill', 

 the main food of many species of whale. The trap proved to contain nothing but ' krill ' and ice crystals, but not 

 intending to return empty handed we collected as many as we could of these pink Crustacea, thinking they would 

 make a surprise dish for David Stratton's birthday next day.^ 



The pink colour and surface occurrence of these animals, which seem to have been large enough 

 for the cooking-pot, suggest strongly they were adult E. superba, although in view of their coastal 

 location (p. 124) the possibility that they could have been the neritic E. crystallorophias must also be 

 kept in mind. 



As far as the permanent, or more or less permanent, ice-fields are concerned we have a number of 

 direct observations, mostly from the Weddell Sea, which, although not very numerous, lead one to 

 suspect that deep inside such regions the numbers of the krill may be much reduced. The more 

 important of these were obtained in January 1932 when 'Discovery II' penetrated the Weddell Sea 

 pack for a distance of approximately 780 miles from 59° S, in 21° W, to 70° S, in 24° W, returning 

 through the ice for approximately the same distance on a north-north-westerly course to South 

 Georgia. As she made her way through the pack shallow (loo-o m.) obUque nets were fished in the 

 pools and lanes of open water that occur in the summer ice, some of the openings being so small 

 that we had to tow on a circular course. The gatherings of the oblique nets examined on this cruise 

 are shown in Table 3. Apart from the moderate catch at Station 818, which was made well south 

 in the East Wind zone, they are very small. Indeed, compared with the enormous catches recorded 

 elsewhere in the East Wind-Weddell surface stream,^ they are meagre to a degree. 



The apparent poverty of the whale food these figures suggest may be directly associated with a 

 corresponding poverty of the diatoms upon which these euphausians feed, for even in summer the 

 great floes characteristic of such ice-fields, some of them as much as a mile or two across, must cut 

 oflF a great deal of light and so greatly reduce the photosynthetic processes essential to a flourishing 

 flora. An alternative explanation may be that in the hub or centre of a clockwise circulation such as 

 exists in this great embayment there is perhaps an eddy or area of slack water where the whale food 



1 Martinez (1951) records that E. superba tastes like shrimp. 



- See Appendix where the average gatherings of the surface population, month by month and sector by sector, are shown 

 for the whole circumpolar sea. 



