ijg DISCOVERY REPORTS 



or mainly within, the broad limits of the 500-250 m. layer. In the same way horizontal nets actually 

 fished at say 15 m., 22 m., 30 m., 38 m. or 49 m., have been taken as having together fished in the 

 layer 50-5 m. Where so many different depths are involved and with a mass of material so large this 

 is the most convenient way of marshalling the data and presenting the broader features of the distribu- 

 tion from the bathymetric point of view. 



The vertical distribution of the staple food of the whales (euphausians over 20 mm. long), based 

 on the total gatherings of the oblique nets, with the data from the surface (0-5 m.) gatherings of the 

 horizontal nets added for comparison, is shown in Table 27. 



Table 27. Vertical distribution of the staple whale food based on the grand total captured in the oblique 

 nets fished between the surface and 2000 m. and in the horizontal nets towed on the surface. Horizontal 

 data in bold roman type, oblique data in italics 



Depth 

 (m.) Total catch Number of hauls Average per haul 



S-o 572.730 412 i»390 



loo-o 555,388 1,622 342 



250-100 423 255 1 



500-250 756 238 3 



1000-500 36g 58 6 



2000-1000 1 13 — 



Table 28. Vertical distribution of the staple whale food in the principal regions of its abundance and 

 scarcity. Horizontal data in bold roman type, oblique data in italics 



Weddell drift. South Georgia and 



Bransfield Strait East Wind drift West Wind drift 



Depth Total Number Average Total Number Average Total Number Average 



[m.) catch of hauls per haul catch of hauls per haul catch of hauls per haul 



5-0 497.532 27s 1,809 66,656 59 1,129 8,542 78 109 



511,281 goy 563 43,158 272 158 949 443 



1 00-0 



2 



250-100 103 101 1 283 44 6 37 110 



500-250 69 90 — 641 64 10 46 84 



1000-500 352 40 8 15 14 -' 24 



2000-1000 1 



2 — — 3 



It is clear from these figures, even from the data provided by the oblique nets alone, that there must 

 be a heavy massing of the krill at levels between 100 m. and the surface, the enormously high average 

 catch-figure for the surface (0-5 m.) zone suggesting strongly that it must in fact be to depths con- 

 siderably less than 100 m. below the surface that the bulk of the population is confined. While Table 27 

 presents the total picture, based on the vast bulk of the material available from the total area in which 

 the whale food (p. 60, Fig. 5 a) is known to range, a regional presentation of the data (Table 28) 

 based on the same material, demonstrates even more emphatically that whether the numbers involved 

 be large or small, whether richly populated regions such as the Weddell system^ or East Wind drift, 

 or sparsely populated regions such as the West Wind drift, be considered, the emphasis is always on 

 the surface zone as being the principal locus of the congregating krill. 



Owing to the rather wide bathymetric horizons through which they are severally hauled the oblique 

 nets cannot of course reveal the finer points of the vertical distribution at levels between the surface 

 and say 250 m. However, the horizontal nets so extensively used on the South Georgia whalmg 



1 That is, the Weddell drift proper together with the Bransfield Strait and the South Georgia whaling grounds to which 

 it penetrates. 



