4 g 2 DISCOVERY REPORTS 



that total immature mortality up to 5 years amounted to about 53 % if the population which the sample 

 represents can be assumed to be stable. 



The relation between the catches and the age structure of the population is briefly discussed, and it 

 is shown that for the segment of the dynamic curve between 9 and 26 years, corresponding to a period 

 when fishing mortality was relatively small, the annual adult mortality rate was probably about 9-2%. 

 The oldest animals in this sample are estimated to have been 42I years old, and it is suggested that 

 the specific longevity of the female fin whale is likely to be about 50 years. 



25. Length-at-age data for area 11 females above 5 years of age are presented, the ages estimated 

 from corpora counts. The von Bertalanffy growth equation has been fitted to this data. This 

 gives a theoretical curve for which l t = 73-0 (i-e -Msa-o-aw)), anc \ corresponds very closely to the 

 observed mean values. This curve has been extrapolated back to 3 years, and is completed by including 

 observed values for foetal growth and the estimated length at age corresponding to weaning. It 

 provides additional evidence of the validity of ovarian corpora counts for age-determination. 



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