OCEANIC MAMMALS 523 



in part proved by the fact that the average length of the total 

 catch in the years from 1930 to 1936 is slowly falling off, with 

 a particularly sharp drop of nearly two feet, in 1934-35, to 

 78.99 feet, or nearly the critical point when the whales become 

 sexually mature. These newly mature individuals are thus 

 killed before they have had opportunity to breed. Further- 

 more, the statistics compiled by Laurie (1937) for the southern 

 stations show in the same years a rapidly rising increase in the 

 proportion of immature females killed, amounting to over 41 

 percent of the total female catch in 1935-36, against nearly 

 half as many in 1932-33. This means not only that an in- 

 creasing proportion of the whales arriving at breeding stage 

 leave no increase, but also that an increasing part of the young 

 animals is destroyed before it attains reproductivity. "The 

 consequences of continued intensive fishing under these con- 

 ditions cannot fail to have a disastrous effect on the future of 

 the stock. When killing has reached the point at which re- 

 cruitment, already dangerously reduced, shall have virtually 

 ceased, one may say that the future of Blue whaling will be 

 limited to the lifetime of those whales now surviving" (Laurie, 

 1937, p. 266). The present i*ate of recruitment is believed 

 insufficient to maintain the stock of blue whales in southern 

 seas under the present intensity of whaling operations. "The 

 stock is already seriously depleted and further hunting on the 

 same scale bids fair to make Blue whales so scarce that they 

 will cease to be a source of profit to the industry and so dimin- 

 ished in numbers that the stock even if completely protected 

 may take many years to recover" (idem). 



Hitherto little progress has been made in remedying these 

 conditions. The only specific protection accorded blue whales 

 by the International Agreement for the Regulation of Whaling, 

 of 1937, is that none shall be killed less than 70 feet in length, 

 thus removing most of the immature animals from the com- 

 mercial class, but since the breeding condition is not reached 

 for females until they attain a length of about 77 or 78 feet, 

 the complete protection of near-breeding stock is not accom- 

 plished. Other general restrictions as to the killing of females 

 accompanied by calves, the limited use of floating "factories," 

 and the limitation of a hunting season to six months in any 

 sector of waters will, it is hoped, prove beneficial, but it is 

 clear that the present wholesale destruction must be reduced 

 in intensity. 



