Kingsford and Hughes Growth, mortality, and size of Acanthochromis polyacanthus 



565 



Figure 2 



Photographs of sectioned Acanthochromis polyacanthus (age = 5 years) 

 otolith showing: (upper) alternating opaque (annuli) and translucent 

 band pattern and (lower) the fluorescent tetracycline mark. Note the 

 single opaque band following the tetracycline mark (time at liberty=380 

 days). OTC = oxytetracline. 



Results 



Age validation 



All fish treated with tetracycline had clear fluorescent 

 marks in their otoliths (Fig. 2). The positions of the 

 fluorescent tetracycline bands in relation to the otolith 

 margin were consistent with the deposition of opaque 

 zones on an annual basis (Table 2). In general, percent 

 agreement was over 75% (7/10 fish). Differences between 

 actual and estimated time at liberty were probably 



related to slight variation in the small measurements 

 that were made (i.e., fractions of a mm). The timing of 

 deposition of the opaque increment was estimated to 

 occur in spring because new increments were found at 

 the edge of otoliths offish that had been marked in May 

 and sacrificed about 200 days later. 



Size and age structures 



There were large differences in the size-frequency dis- 

 tributions of fish sampled across the shelf (Fig. 3). At 



