ON THE STOCK OF WHALES AT 

 SOUTH GEORGIA 



By J. F. G. Wheeler, D.Sc. 

 (Text-figs. 1-3) 



The application of the method of age determination described in a previous paper 

 has brought into prominence the complex nature of the whale population which 

 year after year since 1904 has been attacked by the catchers of the companies operating 

 from South Georgia. Study of the age composition of the population strongly suggests 

 reduction of the stock, and some advance has been made towards ascertaining the rate 

 at which reduction has proceeded. Work on these lines, when considered in relation to 

 other investigations, such as the movements of stock, affords a fair prospect of reaching, 

 in this area at least, a scientific basis for the attainment and maintenance of economic 

 security. 



Several points of interest arose as the results of age determinations were studied. The 

 calculated rate of reduction is not without interest and suggestiveness. Wholly depen- 

 dent as it is upon the unit character of the recurring whale population and carrying 

 within itself evidence that sections, at least, of the population are not present in the area 

 in their true proportion, it provokes consideration of the real nature of the catch and 

 enquiry into the population from which the catch was drawn. 



This paper is an attempt to give the steps by which the calculation of the rate of 

 reduction was made possible and a brief review of the problems underlying the study of 

 whale stocks. 



The treatment of the data had of necessity to be undertaken from a statistical point 

 of view and for this part of the work I am indebted to Mr T. Edser of the Ministry of 

 Agriculture and Fisheries, whose expert advice has been invaluable, and to Mr G. E. R. 

 Deacon of the Discovery staff. I am also grateful to Dr Stanley Kemp, and to Sir Sidney 

 Harmer and Mr J. O. Borley of the Discovery Committee, for much constructive and 

 willing assistance. 



Since 1925 members of the scientific staff of the Discovery Committee have been 

 engaged at South Georgia in an intensive enquiry into the biology of whales, during 

 the course of which a large proportion of the whales brought in for commercial purposes 

 by the Compania Argentina de Pesca has been examined. Following out an indication 

 of a method of age determination given on pp. 450-2 of Southern Blue and Fin Whales 

 (Mackintosh and Wheeler, 1929), a definite correlation was established in season 

 1929-30 between the number of corpora lutea in the ovaries of female Fin whales and 

 physical maturity as indicated by the ankylosis of the vertebral epiphyses to their centra, 

 and further light was thrown on the theory that age can be determined in the females of 

 this species from the number of corpora lutea. These results were put forward in a later 



