141 



EFFECTS OF WHALING ON BALEEN WHALES 



'catcher's day's work', which may be abbreviated to C.D.W. They discuss 

 its advantages and drawbacks as a unit of effort and use it to compare catches 

 in different areas. The main disadvantage is that catcher efficiency has been 

 steadily increasing, so the C.D.W. is not a constant unit of effort (Fig. i), 



her restrictions J 



B.W.U. 



I600O 

 I500O 

 14000 



lOO 



Number of calchers^ 

 (pelagic ' 



50 



1-5 q 



r-o ^ 



0-5 



Zooo 



looo < 

 t300 



1930 



1935 



1940 



1945 

 Years 



1950 



1955 



I960 



Fig. I. — Total antarctic catches of baleen whales; changes in catch quotas; percentage fin whales 

 (of fin and blue); fin whales per C.D.W.; and number of catchers and their average tonnage 

 and power. 



nor has it been possible as yet to correct for the variations. The average gross 

 tonnage and power (LH.P.) of the whale catchers have increased by 165 and 

 216 per cent respectively between 1930-31 and 1958-9- There are other 

 unmeasurable improvements, in navigational aids and the introduction of 

 asdic and helicopters. Diesel engines increase the range and endurance of 

 catchers and lessen their dependence on the factory ship. Other factors such 

 as competition between catchers, improvements in factory machinery, gear 

 saturation (days when more whales are caught than the factory can handle 

 and catching operations are limited to a few hours), and changes in the 



