ijo DISCOVERY REPORTS 



Towards the end of this cruise ' Scoresby ' ran into an area described by Gunther as being of 

 'exceedingly widespread patchiness' a mile or two to the north of Station WS 558 in 57° 41' S, 

 23° 12' W.i Here patches of krill of irregular outline were scattered about haphazard in all directions 

 and were so numerous that in the course of a lo-mile run the observers were sometimes recording 

 them every 10 or 30 sec. The majority were quite small ranging from some a yard or two across 

 to others of from 50 to 100 square yards in area. Larger patches, one of 1800 square yards, were 

 also seen. 



Elsewhere in a posthumous pubUcation Gunther (1949) gives an admirable description of patches 

 he saw while whale-marking off South Georgia in the season 1936-7. 



On nth January whales in the act of feeding came under direct observation. A heavy concentration estimated to 

 number 100-200 whales was centred over a patch of whale food in an area of 4-5 square miles. The krill {Euphausia 

 superba) could be seen in a layer no more than 3 m. below the surface, and in places it affected the colour of the sea. 

 An easterly gale the previous day had left a very heavy swell, but the wind had since moderated and waves were 

 no longer breaking. The sky was grey and the bad visibility was reduced from time to time by patches of mist. 

 The sea was grey too, but in places the krill imparted to it a barely noticeable tinge of ochre. In one place where the 

 krill was unusually thick and might have been closer to the surface a patch of half an acre or so had a brick-red tinge. 

 The krill was irregularly spread over the whole region with large gaps between the swarms; some measured a few 

 feet across and had an indefinite contour like that of a gorse bush, and others extended in long wavy bands from 

 one to several feet or even metres in width. The krill did not seem as dense as patches of it often are, and it looked as 

 though it had been broken up by the recent gale and had been depleted by the depredations of the whales. 



Krill patches are by no means exclusively a feature of the open sea. They have been observed in 

 great profusion in deep embayments of the land, such as Cumberland Bay on the east side of South 

 Georgia, and have commonly been recorded right inshore, sometimes for instance near the Govern- 

 ment Jetty at Grytviken at the head of Cumberland Bay. Farther south at the South Shetlands (p. 41) 

 Webster records their stranding right inside Deception harbour and I have seen them too (Marr, 1937) 

 cast up on the beach in Admiralty Bay. Still farther south in De Gerlache Strait Bagshawe (1938) 

 records E. superba in millions a yard or two from the shore near Andvord Bay. Nor is patchiness 

 confined to the adult population alone. It has been seen in half-grown individuals, in still earUer 

 adolescent forms and, judging from the enormous variation in catch-figures (p. 219, Tables 45-7) 

 revealed by the random sampling of our nets, would appear to be a feature of all developmental stages 

 of this species from hatching onwards. 



Perhaps the strangest situation of all in which the krill has been reported was in a wave-cut cavern 

 in the 120-ft. high Mertz Glacier Tongue, into which Mawson (1942) penetrated for 120 ft. by boat 

 in December 191 3. 'Looking down through the clear blue waters', he writes, 'many shrimps (krill) 

 about an inch in length could be observed swimming about near the surface'. 



When looking down on a krill patch through a metre or two of water one gets the distinct and some- 

 times alarming impression^ that one is seeing the bottom and that the ship has blundered into shallow 

 soundings, and it may well be that a number of the alleged shoals and ' muddy ' patches reported by 

 early navigators in southern waters were in fact sightings of swarms of this, or other closely packmg 

 animals such as (p. 136) Grimothea, not far below the surface. 



Close inspection of a small patch at the jetty at Grytviken revealed it to be in a continual state of 



flux, constantly changing shape, expanding and contracting, elongating this way or that, partially 



dividing only to re-form and become one whole, but never actually breaking up, in a manner distinctly 



amoeboid. An admirable description of this phenomenon is given by Hardy (1935, p. 210) and is 



quoted in full in the section which follows. 



1 Possibly this was part of the same patchy region encountered earlier at Station WS 540. 

 * As Captain Cook's watch-keeper (p. 40) evidently did. 



