Longevity and Mortality Rates of Fish in Nature 157 



It is found that all the growth curves shown in Fig. 2 and, 

 indeed, those for a great many other species of fish, can be 

 adequately represented by the mono-molecular or inverse 

 exponential equation which, in its simplest form, is 



i, = L„(l-e-«) 



(1) 



ISO 



lOO 



L(cm.) 



Acipenser nudiventris 



L(cm) 



Oncorhynchus y 



nerka 



.oreqonus 

 T clupeaformis 



Clupea harenqus 



25 30 



4 5b 



ACE (yr.)- 



Fig. 2. Some examples of curves of growth in length of fish. 



where l^ is the length at age t, L^ is the maximum or asympto- 

 tic length and ^ is a constant which determines the curva- 

 ture of the growth curve, that is, the rate at which the asymp- 

 totic length L^ is approached (see, e.g. von Bertalanffy, 1938; 



