SOUTHERN BLUE AND FIN WHALES: SUMMARY 467 



census is naturally impossible, but there are grounds for anticipating that at least some 

 very rough approximation, sufficient for this purpose, will be achieved in due course. 



Among the features of the habits and general biology of Blue and Fin whales dis- 

 cussed in this section, it would appear that some favour the survival of the stock, while 

 others must be considered serious weaknesses. For instance, the protracted polyoestrous 

 breeding season, the comparative immunity during the breeding processes and nursing 

 of the young, and the rapid growth of the young to sexual maturity, are all to be re- 

 garded with satisfaction. On the other hand, since each female can at the most produce 

 one young every two years the rate of propagation is extremely slow. 



It is difficult to say whether or not the "elasticity" of the breeding season and the 

 natural protection of the whales during the essential stages of the sexual cycle, are 

 sufficient to counterbalance the weakness of the slow rate of propagation, but the killing 

 of a disproportionately large number of immature whales is a separate and very serious 

 matter. 



It is not the object of this memoir to discuss or recommend any definite measures 

 by which the whaling industry should be adjusted, but rather, as a beginning, to bring 

 forward certain facts and inferences about the biology and habits of whales which have 

 a bearing on the effect of hunting on the stock. One thing, however, is perfectly clear, 

 and that is that in proportion to the value of the products obtained, far more damage is 

 done to the stock in temperate and sub-tropical waters, such as at certain South 

 African stations, than is done by the whaling stations and factory ships in the De- 

 pendencies of the Falkland Islands. That is to say, that at these stations where some 

 80 per cent or more of the catches consists of lean immature whales and much of the 

 remaining 20 per cent (or so) includes actively breeding whales, the very maximum of 

 damage is inflicted on the stock, with practically a minimum return in respect of 

 produce. 



It is not suggested that the sub-Antarctic industry has actually less effect on the stock, 

 but here at least a relatively good return is obtained from each whale, and the catches 

 are drawn from a much larger proportion of the classes of whales which can be spared 

 from the stock, 



SUMMARY 



The preceding pages deal with the results of direct investigations on whales carried 

 out at the Marine Biological Station at South Georgia and at Saldanha Bay, South 

 Africa, from 1925 to 1927. During this period a total of 1683 whales was examined, of 

 which 1577 consisted in almost equal numbers of Blue and Fin whales. The present 

 memoir is concerned only with these two species. Similar work is being continued at 

 South Georgia as there is much to be gained by the accumulation of further material. 



The work has been guided by three main objects : 



I. The determination of the characters of southern Blue and Fin whales and the 



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