514 



Fishery Bulletin 92(3). 1994 



Although additional preparation may have increased 

 resolution of rings near the primordia, poor ring reso- 

 lution caused by accessory primordia would probably 

 not have been improved. 



The addition of a constant to asterisci ring counts 

 (6 days) adjusted for the time lag between hatching 

 and otolith formation and was not used to compen- 

 sate for uncounted rings. The addition of constants 

 to estimates of age did not affect the rank of the co- 

 efficients of variation. 



All otolith diameters, especially sagittae, exhibited 

 a strong correlation with fish lengths. This relation 

 can be useful in backcalculating size at age. How- 

 ever, because the ring count did not accurately esti- 

 mate age, accurate ages derived from sagittae can 

 not be associated with back-calculated sizes. The 

 relation between asteriscus diameter and fish length 

 was not as strong as with sagittae, but the improve- 

 ments in accuracy and precision in estimating age 

 would increase the confidence in back-calculated 

 sizes at age. However, because asterisci were not 

 present at hatching, size-at-age information for fish 

 <7 days old could not be backcalculated. Rings formed 

 in the asteriscus were concentric and proportionally 

 spaced throughout the otolith because no accessory 

 primordia were formed, making it straightforward 

 to measure radii or increment widths precisely re- 

 gardless of the chosen axis of measurement. 



We conclude that the asteriscus is the best struc- 

 ture to use in ageing young red drum >4.0 mm SL. 

 Using our sagittal section technique with juveniles, 

 we found that the asterisci clearly provided superior 

 accuracy and precision in ageing. Previous efforts by 

 Peters and McMichael (1987) to age juvenile red 

 drum using transverse sections of sagittae provided 

 reasonable age estimates; however, because they 

 began counts a standard distance from the primor- 

 dium to allow for uncounted rings ( 10), the accuracy 

 and precision of resulting counts on 21-day-old fish 

 cannot be known in the same sense that we estimated 

 these statistics when all rings were counted on 

 asterisci of 46-day-old fish. The advantage of using 

 asterisci is that clear rings can be seen in sagittal 

 sections, and grinding asterisci in the sagittal plane 

 can be done relatively quickly. Furthermore, all rings 

 were visible in the asteriscus, and only adjustment for 

 age at formation was required to estimate true age. 



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