62 



S. J. HOLT 



Table II. — Values of growth and maturity parameters for some fish 



Species 



Tilapia esculenta . 

 Upeneus moliucensis 

 Polydactylus indicus 

 Mugil parsia 

 Clupea pallasii 



Gadus minutus < g 



Melanogrammtis aegkjinus 



Limanda yokohamae < g 



Citharichthys sordidus $ . 



K 



-Loo (cm) 



34 

 i6 

 150 

 40 

 35 

 20 

 23 

 75 

 24 

 29 

 28 



0-67 

 67 

 57 



Sources. 



Garrod (1959). 

 Gottlieb (1959). 

 Mohamed (1955). 

 Sarojini (1957). 

 Japan (i955)- 

 Menon (1950). 



Thompson (1939). 

 Hatanaka & 



Iwahashi (1953). 

 Arora (1951). 



especially in relation to his own experiments with salmonoids, but he did not, 

 to my mind, sufficiently distinguish the different aspects of what is generally 

 referred to as 'growth rate', and recognize that at least two parameters are 

 required to describe normal growth increments and curves. Not only have 

 conclusions as to whether size or age is the chief determinant of maturity 

 often been conflicting for this reason, but there has been considerable dis- 

 cussion of whether the onset of maturity causes changes — usually decreases 

 — in growth rate. This question arises from the observed coincidence 

 between the inflexion in the weight-age curve and the size at maturity (not, 

 of course reflected in the length-age curve). Because maturity frequently 

 occurs at well over half the final length, and often at more than three- 

 quarters of it, it can appear that the growth pattern thereafter is changed 

 whereas the growth curves may in reality be quite smooth and continuous. 



Only for a few fish are published data sufficient for analysis of the relation 

 between growth history and maturity in individuals of the same stock, 

 though /„^ can often be estimated from the width of the first spawning ring 

 on scales, etc., and the preceding growth deduced from the annual ring 

 widths. Very commonly however it is reported that faster growing fish 

 mature at an earlier age than slower growing ones, though they may be 

 absolutely smaller at maturity than the later maturing fish (see e.g. Parker & 

 Larkin, 1959, for Salmo and Oncorhynchus species). Garrod (1959) showed that 

 those Tilapia esculenta in Lake Victoria which mature when relatively small 

 have higher K and lower La, than those which matured at a relatively larger 

 size. There is in his data some evidence that the ratio /m/Loo increases with 

 increasing K. It may be worth noting that in cases such as this, where the 

 values o£K may be in doubt because it is not known whether scale-rings are 

 annual or represent periods less or more than a year, then a relation such as 

 that shown in Fig. i might suggest which of two or more differing values of 

 K is more likely to be the correct one. 



More hght would be thrown on this problem by a study, in a single 



