144 R. M. LAWS 



In view of this changing composition of the catch, and of the progressive 

 increase in catching efficiency, it has not been possible to arrive at any 

 estimate of the absolute increase or decrease in the number of each species 

 of whale caught per constant unit of effort, and so to make a quantitative 

 estimate of the changes in the stocks. I do not think there can be any doubt 

 that the blue whale stocks have suffered very heavy depletion, but the 

 position is less clear with regard to the fm whale. 



Turning again to Fig. i, let us compare the catches of fm whales per 

 C.D.W. from 1950 onwards, with the catcher efficiency. The effect of 

 competition between catchers has been fairly uniform over this period 

 because agreements between the whaling companies have kept the number 

 of catchers at a fairly constant level. The number of fm whales per C.D.W. 

 increased up to 1955-6 and then fell in the subsequent three seasons although 

 the average catcher efficiency continued to improve (I.H.P. increase nearly 

 23 per cent). 



It should be noted that with the opening of the former sanctuary in the 

 Pacific sector, new stocks were exploited and the 'centre of gravity' of 

 whaling in the older areas also shifted. In the 1955-6 season 26*7 per cent 

 of the total pelagic catch of fin whales was taken in these new areas; in 

 1956-7 their contribution was 41-0 per cent and in 1957-8 it was 23-7 per 

 cent. In 1958-9 it dropped to 8-2 per cent. The catch of fin whales per 

 C.D.W. in this area (I and VI combined) was 1-99 in 1955-6, the highest 

 ever recorded in any area, and subsequently declined greatly. Blue whales 

 were not abundant there. 



For three seasons then, the opening of the sanctuary, as was intended, 

 relieved the pressure on the other stocks of whales. The rise in the value of 

 fm whales per C.D.W. in 1955-6 was probably partly a result of this, and 

 the stabihzation and decline of the figures for fin whales per C.D.W. should 

 otherwise have become apparent earlier. The later opening date for the 

 catching of blue whales probably also contributed to this. I have also calcu- 

 lated the values for 'sexually mature' fm whales per C.D.W. (that is females 

 above 64 ft and males above 62 ft in length) and have plotted them in Fig. i. 

 These show a more marked decline, beginning after i953-4» suggesting a 

 differential decrease in the numbers of older animals. I will return to this 

 point later. 



The values for fm whales per C.D.W. considered separately for the 

 various whaling areas I-VI show a similar relative stability or decline, most 

 marked in the newly exploited stocks in areas I and VI which have always 

 been considered to be numerically small compared with other areas. The 

 data for area III show a rapid increase in fin whales per C.D.W. up to i • 54 

 in 1952-3 and subsequently a slight but noticeable increase up to 1-72 in 



