LOCAL DISTRIBUTION. THE SOUTH GEORGIA WHALING GROUNDS 421 



The massing of the whale food on the north-eastern side of the island under the influence of the 

 branching Weddell stream is emphasised over and over again by the monthly distribution of the large 

 rorquals taken by the South Georgia whalers, the charts of Kemp and Bennett (1932) for the period 

 1923-31 revealing repeatedly such an enormous preponderance of blue and fin whale kills in the 

 eastern branch of the current that there can be little doubt that they congregate there because of the 

 exceptional richness of their food. As Ruud too (1932) remarks, 'it seems reasonable to suppose 

 that the whales regularly seek out the places where the krill occur in the greatest profusion '. 



With regard to this local but most striking distributional link-up Kemp and Bennett write as follows : 



That the principal whaling grounds lie to the north-east of South Georgia is to be explained on hydrological grounds. 

 It is due to the system of currents which prevails in the neighbourhood of the island. One of the currents, which 

 comes from the Pacific, flows through Drake Passage to the south of Cape Horn, and taking a north-easterly direction 

 passes to the west of South Georgia. As it progresses northwards it comes more and more within the influence 

 of the westerly winds and thus tends to take a more easterly course. The second and more important current is of 

 Weddell Sea origin. It passes round the south-eastern end of South Georgia and then sweeps in a north-westerly 

 direction along the coast. Before, however, it reaches the northern end of the land it meets the first current and the 

 prevailing westerly winds and is reflected backwards to take a north-easterly course. The direction of the Weddell 

 current is thus largely due to the presence of South Georgia and to the position which the island occupies athwart 

 the region where the two streams converge. 



Euphausia superba, the exclusive food of Blue and Fin whales in the Antarctic, is a pelagic prawn which drifts 

 northwards to South Georgia from higher latitudes, the greater part coming from the Weddell area. The whaling 

 grounds lie in the lee [i.e. on the north-east side] of South Georgia, and it is here, in the shelter of the island, that 

 the Euphausians are able to congregate. 



Another striking example of distributional linkage between krill and predator in this locality is 

 provided, it seems, by the large adult Nototheniid, and prodigious krill-eater, Notothenia rossii, which 

 according to Olsen's findings (1954) is heavily massed throughout the whole of the shelf water along 

 the north-east side of the island, but absent from the wide krill-poor shelf area to the south-west. 



The monthly developmental condition of the swarms in the main east-flowing Weddell stream 

 compared with the corresponding condition of the swarms in the neighbourhood of South Georgia 

 is shown in Fig. 156. This diagram, constructed on precisely the same lines as Fig. 55 (p. 253), 

 is presented principally to show that there is no mass spawning of the krill in the South Georgia 

 area and that the rich euphausian population there cannot, therefore, be of local origin but must in 

 the main be derived from the swarms that spring from the widespread larval risings that take place in 

 Weddell West and subsequently get carried to the island in the surface drift. 



The absence of concentrations of eggs coupled with, even more important still, the absence of 

 swarms with a naupliar or metanaupliar mode, provides the principal evidence of the absence of a 

 local spawning, although almost equally conclusive evidence is provided by the extreme rarity with 

 which substantial surface swarms of slightly older denomination (the Calyptopes for instance) have 

 been recorded in these waters throughout the maximum period, November to March, over which 

 spawning is known to be spread. As Figs. 148 and 150 show, the vast majority of our observations 

 between January and March, whether with vertical or stramin nets, record only negligible numbers of 

 young surface forms. Even moderate samples are rare, gatherings of between 100 and 1000 individuals 

 such as we get so regularly at this time in the Weddell stream, and which in the vertical nets at least 

 probably represent the effective sampling of a swarm, having been recorded only twice in the vertical 

 and only thrice in the stramin nets. 



While it seems fairly clear that the populating of these island waters must be brought about through 

 the incursion of alien swarms from the Weddell Sea, owing to a gap in our observations in this other- 

 wise heavily sampled region we have no precise information as to just when such incursions first begin 



