PLANKTON AND WHALE DISTRIBUTION 273 



PART V. THE PLANKTON COMMUNITY, 



THE WHALE FISHERIES, AND THE HYPOTHESIS 



OF ANIMAL EXCLUSION 



By A. C. Hardy, m.a. 1 



PLANKTON AND WHALE DISTRIBUTION 



One of the objects in undertaking these investigations was an attempt to obtain a 

 better understanding of the natural history of the great plankton-feeding rorquals 

 — the Blue and Fin whales. We have seen that they have been shown by Mackintosh and 

 Wheeler (1929) and others to feed in this area exclusively upon the one species of Euphau- 

 sian, E. superba. It is important to know how closely the distribution of these whales is 

 correlated with that of their food supply. Naturally some correlation with the distribu- 

 tion of their food is to be expected ; but if the whales are not continually feeding, there 

 may be other important factors governing their movements. The degree of correlation 

 between the distribution of the whales and Euphausians should give some measure of 

 the relative importance of food as compared with that of other factors which are as yet 

 unknown. A very close correlation over a number of seasons would indicate the pre- 

 eminent importance of the plankton as a factor determining the location of the fisheries. 



Recently Kemp and Bennett (1932) have published a report on the distribution of the 

 Blue and Fin whales at South Georgia and the South Shetlands based on returns sent 

 in by the industry on forms specially provided. They chart the monthly distribution of 

 whales taken in the South Georgia fisheries for the seasons 1923-4 to 1930-1, and the 

 South Shetlands fishery for the seasons 1922-3 to 1928-9. They have kindly allowed us 

 in this section to reproduce a number of their charts. In Fig. 141 are shown the distribu- 

 tion of Fin and Blue whales round South Georgia in December 1926, together with the 

 distribution of E. superba during the plankton survey in the latter half of December and 

 early January. It is seen that the correlation with both species of whale is a fairly close one. 



Since the whaling stations and floating factories were all situated in the fjords of the 

 north-east coast one might expect the majority of whales to be taken in the region close 

 to these stations if they were at all evenly distributed round the island, and this might 

 give rise to an apparent but false correlation, but a reference to Fig. 142 will show that 

 the whales are not always taken off this coast, and at times the whalers have to go far 

 from the stations in search of them. 



Fig. 143 shows the distribution of Blue and Fin whales in March 1926. They are 



concentrated in a small area against the coast quite different from their distribution in 



December 1926. In March 1926 we began our plankton investigations in the area. As 



already explained, it was impossible owing to the lateness of the season and a succession 



of gales to survey more than a limited region off this coast, but as far as it went this 



survey showed that the E. superba were also concentrated at this time close against the 



1 I am indebted to the many friends with whom I have discussed the arguments put forward in this 

 section, particularly to my colleague Mr E. R. Gunther who wishes it to be known that he is in complete 

 agreement with the conclusions that I have reached. 



