THE STOCK OF WHALES AT SOUTH GEORGIA 355 



figures given, although not impressively numerous, demonstrate this rapid diminution. 

 If the catch of a single season were sufficiently large, or if examination could have been 

 made of all the female Fin whales brought in to all the stations during a single season 

 the sample would have been nearer the ideal. In the circumstances the figures for several 

 seasons have been taken together and considered as a unit, although it is realized that 

 changes may have occurred in the size of the stock and the intensity of fishing from 

 season to season during the period of investigation to make the calculated rate of reduc- 

 tion only an approximation. It is, for instance, likely that the last two seasons were 

 adversely affected by the pelagic fishery to the south and east of the island ; and as in 

 these seasons a greater percentage of the whales brought in was examined, the rate of 

 reduction will be unduly weighted by them. The proportion of the catch we examined, 

 however, was a random sample of the catch of the Pesca company, since, when whales 

 were missed, no selection was made. Our sample should be therefore just as representa- 

 tive of the local population as the slightly larger Pesca catch. The over- weighting 

 of the later seasons will certainly affect the rate of reduction if the stock is attacked 

 elsewhere, but that is part of the disability of treating several seasons together, and 

 if the damage has been done, then the calculated rate of reduction is more closely 

 applicable to present day conditions than it would be if the earlier seasons alone were 

 considered. 



The missing of whales here and there during the season cannot affect the sample 

 when no selection is made, but the absence of observations for a considerable part of 

 the season is a different matter. Partial catches are not admissible in the analysis of age- 

 group reduction since fluctuations are known to occur during the season not only be- 

 tween the numbers of each species present on the grounds but also between the numbers 

 of each sex and stage of maturity of each species. Thus in Southern Blue and Fin Whales 

 (p. 460) it is remarked that "when the first and second halves of a season at South 

 Georgia are compared it is found that in the first half the catch is composed of a majority 

 of mature whales, while in the second there is an influx of immature whales (and per- 

 haps a withdrawal of adults) which causes a sharp reduction in the average lengths " and 

 again "Apart from the fact that immature whales have occurred in relatively greater 

 numbers in the latter part of the season, there is an indication that of the adult whales 

 themselves, those taken early in the season are mostly older than those taken later". 

 This is shown very clearly in Fig. 1 in which physical maturity has been used as a dis- 

 tinguishing character contrasted with early sexual maturity and sexual immaturity. 

 Over five complete seasons the majority of physically mature females appeared in 

 December, the majority of sexually mature not physically mature females in January 

 and the peak of the influx of immatures was in February. 



In seasons 1924-5 and 1927-8 observations were not commenced until well into the 

 second half of the season, consequently the figures for these seasons must be neglected 

 in the consideration of stock reduction since in both the proportion of the younger 

 section of the population will be abnormal. The number of whales is now reduced by 

 41 to 431. 



