COMPARATIVE POPULATION STUDIES IN FISHERY BIOLOGY 63 



Fig. I. — Values of the growth parameter, K, plotted against a transformation of the ratio of 

 length at maturity to asymptotic length. 



Closed circles: Data from Beverton & Holt (1959) for many different fish species. 



Open circles: From Holt (i959^) for mackerels. 



Crosses: From Holt (1959^) for sardines and related species. 



Triangles: Various other fish species, see Table II. 



cohort, of the relations between Im, L^ and K for individual fish, back- 

 calculated from scales or other hard structures. At the same time it may be 

 necessary to examine the mortality rates in subclasses of that cohort in which 

 are grouped fish with the same growth patterns, it being remembered that 

 the mean age of maturity is affected by the value of total mortahty in the age 

 range over which maturation occurs,^ and that neither the natural nor the 

 fishing mortahty rates of late maturing fish are necessarily the same as those 

 of the early maturing ones. 



It will now be apparent that if K were known a rather better estimate 

 could be made of L^ from measurements of /,„. The required knowledge of 

 K might come from tagging or rearing experiments. In practice care would 

 have to be exercised because it seems that K may vary with environmental 

 conditions, and particularly with temperature. Thus, Taylor (1958, I959) has 

 shown that K increases with increasing temperature in cod {Gadus morhua) 



