50 



Fishery Bulletin 92(1). 1994 



countings performed on whole and sectioned otoliths 

 showed that, in the sub-sample analysed, the Index 

 Average Percent Error (IAPE) of Beamish and 

 Fournier (1981), was lower for counts performed on 

 whole (6.7%) than for counts performed on sectioned 

 otoliths (12.1%). For the total sample, where read- 

 ings from whole and sectioned otoliths were inte- 

 grated, the IAPE was reduced to 5.1%. 



Otolith growth 



Otolith weight was directly related to age and an 

 exponential function offish length (Fig. 3). Within 

 each age class, otolith weight was positively corre- 

 lated with fork length for most classes (Table 1), 

 indicating a tendency for larger fish to have larger 



100 



10 20 30 40 50 60 70 



Fork Length (cm) 



E 



5 



I0U 



Figure 3 



Relation between otolith weight and Fork Length 

 (FL) and otolith weight and age for coral trout, 

 P. leopardus. 



otoliths than smaller fish of the same age. The 

 weight of the otolith was a good predictor of age and 

 accounted alone for 89%> of the variability in age of 

 the coral trout (r^O.889, P<0.0001), with fork length 

 accounting for 1.5% (partial r 2 = 0.015). Otolith 

 weight was a function of age and fish size, as indi- 

 cated by the results of the multiple regression fit- 

 ting. The interaction between age and fork length 

 alone accounted for 89% of the variability (r-^0.892, 

 P<0.0001) 



Validation of annulus formation 



All fishes treated with tetracycline displayed clear 

 fluorescent marks in their otoliths (Fig. 4). The re- 

 sults obtained for recaptured and captive fish, rang- 

 ing in age from one to eight years, showed that 

 annuli are formed once per year (Fig. 5). The first 

 annulus is formed in the otoliths of the juvenile coral 

 trout during their first year of life (Fig. 6). The rela- 

 tive positions of the fluorescent bands, in relation 

 to the otolith margin and the translucent and 

 opaque zones (annuli), indicated that the formation 

 of the annulus occurred mainly during winter and 

 early spring (Figs. 5 and 6). 



Growth model 



The samples obtained from line-fishing and spear- 

 fishing were selective towards individuals larger than 

 25 cm FL. Consequently, the 0+ age class was not rep- 

 resented in this sample and the age-1 year class was 

 represented by only four individuals (Fig. 7). The 

 sample collected with fence nets, composed of indi- 

 viduals from the smaller size classes, consisted to- 

 tally of individuals of the 0+ and 1+ year classes 

 (Fig. 7). Table 2 shows the results obtained when 

 fitting the growth model to the data including all 

 age classes and to the data including only age >2+. 



