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R. J. H. Beverton and S. J. Holt 



fact, a considerable amount of data on the size at which fish 

 first reach maturity, and we have investigated whether the 

 average length at which maturation occurs (L„J in relation to 

 the asymptotic length (L^) has any bearing on longevity. 

 Thus, in the last column of Table I are given the ratios LJL^ 

 and in Fig. 8 these are plotted against maximum age, T 

 The points are very much scattered, although there is perhaps 



00> 



max* 



Lm 



L CO 



10 



20 30 



— T max (yr ) — 



40 



50 



Fig, 8. Size at maturity (L^) and longevity. Plot of ratio LmjLco 

 against Tmax- • = Salmonoidei, x = Clupeoidei; other species 



shown as Q • 



just a hint that the shortest-lived species are those which have, 

 on average, the highest value of LJL^, that is, mature at a 

 relatively late stage in their growth cycle. This tendency is a 

 little clearer within the salmonoid group (solid circles), but in 

 the clupeoids (crosses), with one doubtful exception, the 

 values of LJL^ are consistently high and have no trend at all. 

 It may, of course, be that this way of relating maturity and 

 longevity is too crude; maturation size might better be ex- 

 pressed, for example, as a function of both K and L^, but this 

 needs further examination. 



