4i6 DISCOVERY REPORTS 



The above, in so far as the principal carrier of the krill and its larvae are concerned, is the hydrology 

 expressed in its simplest terms. The actual conditions, of course, are far more complex. South Georgia 

 lying in a region of converging water masses in which waters of Bellingshausen Sea, West Wind and 

 Weddell origin are all involved. Broadly, however, it is evident that the north-east side of the island 

 is much more widely aifected by the Weddell stream than the south-west side, and this being so we 

 should expect to find, the Weddell current being the important carrier it is, that the distribution 

 of the krill in this locality would correspond with the major aspects of the distribution of the 



Fig. 147. Branching of the Weddell stream in the neighbourhood of South Georgia, showing major influence of the 

 current on the north-east side of the island (after Deacon, 1933 and 1937). 



Weddell water as simply outlined here. And this, as Figs. 148-55 show, is precisely in fact what our 

 observations repeatedly reveal, the krill in all phases of their surface development and at all times 

 of the year our observations cover being found massed conspicuously off the north-east coast and 

 for the most part absent or virtually absent from a wide area extending far to the south-west of 

 the island. In this south-western backwater as it may be called, throughout the long course of the 

 observations conducted there, only two substantial catches of whale food have been recorded. 

 Both were obtained in spring (Figs. 152 and 154), the swarms encountered (p. 370, Fig. 118, 

 Stations 517 and 523) consisting of young adolescents approximately one year old. Exceptions, 

 however, are always to be expected, hydrological boundaries being variable and doubtless 

 shifting their position from time to time with changes of wind and other factors. It may too be 

 significant that both gatherings were recorded at the end of spring, late in November, when 

 the volume of Weddell water reaching South Georgia is possibly augmented by the melting of the 

 not far distant pack. As Wordie and Kemp (1933) remark of this region, the currents are strongest 

 in spring. 



In the plankton survey of 1926-7 Hardy and Gunther (1935, p. 212, Fig. 92; Hardy, 1928, Fig. 4) 

 also show a conspicuous massing of the whale food on the north-east side of the island and an equally 

 conspicuous scarcity or absence of it off the south-western and southern coasts. Hardy (1935, 

 pp. 273-322) explains this in terms of his Hypothesis of Animal Exclusion (p. 216) arguing from the 

 fact that a dense belt of phytoplankton along the south-western and southern sides of the island 

 coincided that season with the region of pronounced euphausian barrenness recorded then. The simple 

 hydrological explanation, however, seems to me to be the more likely one, just as it seems to explain 

 the massing of the krill in the East Wind- Weddell surface stream as a whole. 



