The Distribution of Senescence 



increase in the size of the prey taken (Frost, 1 954). Ricker (1945) 

 comments that 'senile death is an everyday occurrence' in popu- 

 lation-studies of the Indiana sun fish. This conclusion is, how- 



Fig. 16. — Growth of trout in Windermere and the small tarns (Frost and 



Smyly, 1952) 



ever, based upon the failure of known sources of death (disease 

 and predation) to account for the disappearance of fish. The 

 overall mortality rates actually found in marking experiments 

 were 56 per cent for small and 58 per cent for older specimens. 



71 



