FISHERY BULLETIN: VOL. 87, NO. 1 



mm SL (see Figure 4), and from estimated ages of 

 3-53 days old. The increments were easily read in 

 most otoliths; only 24 larvae were rejected due to 

 either the error in reading precision being greater 

 than 2 for the sagittae of a larva (10, 2.5%) or be- 

 cause otoliths could not be clearly read (14, 3.5%). 

 The plot of standard length (SL) against sagittae 

 maximum radius (OD) revealed a logarithmic rela- 

 tionship (Fig. 3). Otolith diameter data were log,, 

 transformed, and a regression equation fitted to the 

 transformed data. This equation is described by 



SL = 5.61.log, OD - 10.56 



(n = 378; F = 2156; P < 0.0001; r' = 0.85). 



Comparison of means from observed and predicted 

 standard length values suggested that any bias 

 caused by log,.-transforming otolith diameter was 

 neglible. 



Validation of Ageing Technique 



Increments were deposited daily in the sagittae 

 of the six larval H. castelnaui kept under ambient 

 conditions in the laboratory (Table 2). When viewed 

 under natural light, a mean of 10 increments were 

 visible from the fluorescent band to the margin of 

 the sagittae. This corresponded to the number of 

 nights that the fish were held after the tetracycline 

 treatment. 



Larval Age and Growth 



It was assumed that the first otolith increment 

 was laid down at hatching (see Discussion); there- 

 fore, the age ofH. castelnaui larvae was estimated 

 directly from the number of growrth increments in 

 the sagittae. Ages were thus minimum estimates for 

 any given length. Descriptions of growth of larval 

 H. castelnaui were based on age-at-length of 378 



25.0 n 



t 20.0 



X 



^ 15.0 ^ 



Q 



< 



Q 



< 



I— 



10.0 



5.0 



0.0 



M I 11 M I I I I I I I I M I I I I I I I M I I I I I I I I M I I I I I I I I I I I I I I I I I I I M I I I 



0.0 50.0 100.0 150.0 200.0 250.0 300.0 



SAGITTA MAXIMUM RADIUS (um 



Figure 3.— Relationship between standard length and radius of sagittae for larval Herklotsichthys castelnaui, 

 together with fitted logarithmic growth curve. 



78 



