274 



DISCOVERY REPORTS 



TABLE V 

 Percentages of marked whales killed 



The Blue whale is the species most eagerly sought after by the whalers, and the 

 percentage figures show how the stock of Blue whales is being depleted at a considerably 

 faster rate than that of Fins, 5 per cent of the marked Blue whales have been killed as 

 opposed to 3 per cent of the marked Fin whales. When these figures are compared with 

 the percentage of marked Humpbacks killed it is at once evident that the Humpback is 

 being slaughtered at a surprisingly greater rate than either the Fin or the Blue ; more than 

 twice as fast as the Fin and much faster than the Blue. Marking has shown that the 

 Humpback whales exploited off the north-west coast of Australia and off the south coast 

 of Madagascar during the southern winter are the same as those upon which a toll has 

 been levied only a few months previously in the Antarctic. The effect of this double 

 persecution on what is quite a small total stock is well shown by the high percentage 

 return of marks, indicating that the Humpback stock is suffering far more even than the 

 Blue, which is itself, on other grounds, regarded as overtaxed (Laurie, 1937). 



In this paper no attempt has been made to explain the impulses of whale movement 

 which it may be possible to find, when further data are available, in such factors as food 

 distribution, hydrological conditions, currents, bathymetrical features, and so on. The 

 stream of Fin whales passing the Shag Rocks on their way southwards and their possible 

 concentration in the western part of the mouth of the Weddell Sea in the latter part of 

 the season may arise, as suggested earlier, from the form of the submarine ridges in these 

 localities ; the westward movement during the season of Blue whales from Enderby Land 

 may have its origin in some current or ice disposition in this region, but at this stage 

 even these tentative suggestions can hardly be made. 



SUMMARY 



1 . Descriptions of the marks used and of the final successful form evolved are given. 



2. Small alterations and additions made to the whale-marking craft and the methods 

 of recording the results of shooting are described. 



3. The scope and result of each whale-marking cruise and the method used to 

 determine the number of whales marked are outlined. 



4. The distribution of the whales marked is briefly discussed and diagrammatically 

 depicted. 



