414 WHALES 



be sure that our 1,000 specimens were, in fact, a random sample (i.e. a 

 sample that is truly representative and not selected in any special way) 

 of the annual catch, and that the annual catch, in turn, is truly represen- 

 tative of the total popvilation. In other words, the percentages of the 

 various age-groups, from the youngest to the oldest, must accurately 

 reflect the corresponding percentages in the annual catch, which, in turn, 

 must reflect the percentages of the total population. This mvist be done by 

 considering the size limit. From the degi'ee of correspondence of the length 

 distribution of the catch on the one hand, and the sample on the other, we 

 can decide if the sample is in fact a random sample of the catch. It is, 

 however, unlikely that the catch, in turn, is a random sample of the total 

 population. While some biologists believe that, undersized animals apart, 

 the catch is in fact representative, especially since, in view of present- 

 day keen competition, gunners have no time to select particularly large 

 and fat specimens and shoot at whatever comes in sight, others believe 

 that what does come in sight first is the younger specimens which are less 

 suspicious of ships (see p. 184), so that the catch consists of a preponderance 

 of younger animals. No wonder, therefore, that some recent calculating on 

 the death rate of individual age groups are not generally accepted. 



Recently, some biologists have tried to establish whether the Rorqual 

 population is static or not by theoretical calculations. To do so, they 

 estimate the population at the beginning of a particvilar year, and then 

 add the expected annual increase and deduct the expected deaths from 

 natural causes and the annual catch. Such calculations have been made, 

 inter alia, with respect to Fin Whales by Prof P. Ottestad (Norway) and 

 Dr E. F. Drion (Holland), whose results were, however, discordant, since 

 they made different estimates of the original population and of the annual 

 death rate. 



Ottestad based his estimates on the assumption that, in 1910, when 

 Antarctic whaling first began, the Antarctic Rorqual population was 

 constant and at its maximum. Now this assumption seems reasonable if 

 we consider that, unlike other animals, whales have few natural enemies 

 and apparently no lack of food. This being the case, we can establish what 

 the annual death rate must be to keep the population static. The moment 

 whaling began, death by capture must naturally be added to death from 

 natural causes, and the total population will therefore have decreased. 

 From what we know of other game, however, hunting may cause the 

 number of births to increase and the number of deaths from natural 

 causes to decrease, since, by increasing the space available for the sur- 

 viving animals, hunters provide them with more food, and enable them 

 to grow stronger and to produce stronger offspring, more capable of 

 resisting enemies and other adverse circumstances. This was shown very 



