54 



Fishery Bulletin 92(1), 1994 



20 



10 



3 

 — 



DS 



-10 



-20 



B     



'■'Ii! ::■■■ 



-2 



10 



13 



16 



Age (years) 



Figure 8 



Von Bertalanffy growth curve fitted to length-at-age 

 data of all age classes of coral trout, P. leopardus, 

 and plot of residuals. 



seems to be the case for age class 2+, the length of 

 which is underestimated by the model including all 

 data (Fig. 8). Exclusion of younger ages under these 

 circumstances would further enhance the underes- 

 timation of K, as well as overestimation of L^ 

 (Mulligan and Leaman, 1992). 



Recent research has suggested the possibility of 

 different growth processes within a population with 

 associated selective fishing mortality (Parma and 

 Deriso, 1990) and natural mortality (Mulligan and 



Leaman, 1992). The large variability in size at a 

 given age observed for the coral trout suggests the 

 occurrence of individual variability in growth. The 

 reliability of methods of growth estimation like 

 length-frequency analysis and growth increments 

 from marking-recapture techniques, is greatly af- 

 fected by this kind of variation (Sainsbury, 1980), 

 further enhancing the importance of obtaining vali- 

 dated length-at-age estimates for exploited fish 

 populations. The results of selective mortality are 

 a direct effect of growth variability on the dynam- 

 ics of abundance, and failure to consider the effects 



