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



which can be used to examine this question, but those we 

 have seen suggest that in this case also a high value of K is 

 associated with both a low L^ and a high mortality. This can 

 be seen for Gadus minutus in Table I, and there is other 

 scattered — but usually incomplete — evidence pointing in the 

 same direction. Thus the grayling {Thymallus signifer) has a 

 higher K and lower L^ in Michigan lakes (warmer) than in the 

 Great Bear Lake (colder) and it apparently lives about twice 

 as long in the latter locality as in the former (Brown, 1943; 

 Miller, 1946). It is said that in France, where it grows fast, 

 the stickleback (Gasterosteus aculeatus) lives only 14-18 

 months, whereas in northern Europe it lives much longer, and 

 indeed does not mature until it is several years old (Bertin, 

 1925) ; according to Flower (1935), sardines (Sardinapilchardus) 

 grow more slowly and live longer in the English Channel than 

 in the south of the Bay of Biscay; and so on. Jenkins, Elkin 

 and Finnell (1955) studied the growth of six species of sunfish 

 (Lepomis spp. and Chaenohryttus) in over one hundred water 

 bodies in Oklahoma and noted for each species that the oldest 

 individuals were always in the populations having the slowest 

 growth rates. We have to be careful in interpreting data of 

 this kind, however, because a general observation that the 

 maximum age attained is lowest in areas where growth is 

 fastest may sometimes be due to effects of fishing coupled 

 with a density-dependent growth rate, the fishing causing a 

 reduced survival and population density and so permitting a 

 better supply of food per fish with a consequent increase in 

 the growth rate (see, for example Fry, 1936, for populations 

 of Hesperoleiicus venustus in Calif ornian streams). 



It is interesting to note that the same associations we have 

 recorded above between growth and longevity in related 

 species, or even in populations of the same species which 

 have become established as independent units in different 

 water basins, do not necessarily hold when growth is modified 

 experimentally. There is not much information on this, but 

 the studies of Aim (1946) on perch populations with stunted 



