Longevity and Mortality Rates of Fish in Nature 143 



influenced the shape of the survival curves and the maximum 

 age recorded in samples. There are, nevertheless, a certain 

 number of instances in which the natural age composition, or 



2- 



O 5 lO 15 20 



Fig. 1. Some examples of survival curves in relatively unexploited fish 



populations. 



something fairly close to it, has been determined, and some 

 examples of these are shown in Fig. 1. It will be noted that in 

 no case do the data cover the whole lifespan from birth on- 

 wards ; this is because representative sampling of the fry and 



