i6o 



DISCOVERY REPORTS 



Table 3 1 . Staple whale food gatherings of more than ten recorded at all subsurface levels examined 

 belozv 5 m. Night gatherings in roman type, day gatherings in italics, the number of night and day hauls 

 made at each depth interval being shozm in the column on the right 



Depth (w.) 



Night 2364, 46, 24 



Day 1237, 990, 697, 697, go, 43 



Night 1 108, 984, 642, 266, 70, 50, 32, 25, 18 



Day 3570, 1500, 450, 426, 348, 2S9, 216, 202, 140, 137, 134, 124, 94, 92, 55, 38, 32, 25, 23, 22, 17 



Night 151, 71, 53, 37, 37, 36, 29, 27, 27, 19, 17, 17, 16 



Day 510, 454, 370, 336, 163, 123, 78, 73, 73, 60, 50, 41, 37, 32, 16,12, 



Night 324, 189, 27, 25, 24 



50-S 



100-50 



250-100 



500-250 



14 



23 



65 



137 



146 



193 



104 



50 



34 

 20 



2 



8 



Krill in small numbers are occasionally taken in the 70-cm. diameter vertical nets, the frequency of 

 their capture as might be expected being highest in the 50-0 m., 100-50 m. and 250-100 m. layers. 

 The vast majority of these vertical gatherings, however, consisting as they do merely of one or tvs^o 

 individuals,^ are too small to provide any reliable information as to the vertical distribution and only 

 two of relatively outstanding size, out of the huge total of vertical samples examined, can be regarded 

 as throwing any light on the matter. They were obtained at Station 1720, where 91 were taken in the 

 100-50 m. net, and at Station 356, where 95 were taken in the 250-100 m. net. While there is no 

 knowing how the krill were actually distributed within these layers, if, like the surface patches (p. 149), 

 they had been disposed in shallow rafts, no more than say a yard or two thick, through which the nets 

 passed for only a second or two, then the numbers recorded at both stations might be regarded as 

 representing clear instances of subsurface concentration in some unknown but perhaps not incon- 

 siderable density. 



Finally, it may well be that the subsurface scarcity of the whale food we seem to find is even greater 

 than our nets reveal. There can, for instance, be no absolute certainty when shooting open nets at 

 night that a catch purporting to come from some deeper level, say 50 or 100 m., was not actually 

 made, or at any rate largely contributed to, at the surface itself, as the net, shot open, let us imagine 

 into a heavy concentration of krill, was momentarily checked to ensure that it was streaming well 

 away and clear of the warp before being paid out to the depth required. For if with the momentary 

 dipping of a hand net several hundred euphausians can be taken from a surface swarm it is manifestly 

 possible that in the second or two, or possibly even longer, that the much larger stramin net must be 



^ Referring to the standing crop of zooplankton in Weddell East Foxton (1956) remarks that except in its young stages 

 E. superba is too 'large and active to be caught regularly by the N70 V, so that the volumes from stations in this region repre- 

 sent the standing crop of zooplankton other than the older krill'. 



