EUPHAUSIACEA 211 



Other swarms were recorded by fishing parties out by the kelp at the entrance of the harbour and 

 on another day we had a similar swarm close to the ship in mid-harbour, just a few hundred yards 

 from the whaling station itself. They were half-grown specimens just developing their reproductive 

 organs. . . . 



It may be mentioned that farther to the south in the Bransfield Strait — not included 

 in the present report — we obtained abundant evidence from a series of consecutive net 

 hauls of the patchiness of very young E. saperba. 



Whilst a vertical diurnal migration of this species is not so well marked as in E.frigida 

 or E. triacantha, there is nevertheless evidence that such a migration frequently although 

 not invariably takes place. This is fully discussed in the special section dealing with 

 vertical migration on p. 237 and illustrated in Fig. 127. Unlike the other two species, 

 which may sink almost entirely out of range of the N 100 H nets, E. superba is more 

 confined to the upper cold water layer, i.e. between the surface and 200 m. Thus the 

 effect of night stations on our knowledge of its distribution is not so marked as it was 

 in the case of the other two species. Its range of depth may be to some extent 

 gauged by the results of the N 70 V nets, although these nets only occasionally capture 

 the species and in small numbers. Except for two occasions, to be mentioned later, at 

 stations across the line of Antarctic Convergence, it was never taken in the N 70 V nets 

 below 100 m. — but 19 specimens were taken in the nets from 50-0 m. and eight in the 

 nets from 100-50. 



We will now describe the distribution of E. superba at the different seasons and regions 

 within the survey. As already explained the N 100 H nets were not used at the oceanic 

 stations approaching South Georgia from the north-east in February 1926, so that we 

 cannot gauge its occurrence on this line ; but we know of its presence at any rate in small 

 numbers from four specimens taken with the N70 V net at St. 11 at a depth of 500- 

 250 m. This was in the cold layer which had dipped below the warm sub-Antarctic 

 surface water. The temperature at 250 m. was 1-08° C. and at 500 m. 2-02° C. 



Off the north-east coast in March and April 1926 the N 100 H nets were towed for 

 three miles on each occasion, so that the effect of patchiness was more likely to be 

 eliminated than in the later stations of the survey when the nets were only towed for 

 1 mile. But by towing for even 1 mile we see by reference to the consecutive net series 

 described on p. 254 that one is more likely to strike a patch than not, and three nets were 

 always towed at three different levels. The E. superba was particularly abundant at a 

 distance of some 20 miles from the coast, and absent from or present in small numbers at 

 the outlying stations. This is shown in Fig. 92. 



In the same region in November 1926 it was only taken in small numbers. 



In the December- January Survey 1926-7 it occurred again in enormous numbers off 

 the north-east coast particularly — in contrast to the preceding March — over the edge of 

 the continental shelf, as many as 42,500 being taken at one station. At those stations 

 taken to the north and east it was present at every station but two, whilst to the west, 

 south and south-east, in marked contrast, it was taken at only five out of nineteen 

 stations and at none of these five stations was it really abundant (Fig. 92). This distribu- 

 tion will be further discussed in relation to the principle of animal exclusion in a later part . 



