Differences Between the Sagitta, Lapillus, and Asteriscus in Estimating Age and Growth in Juvenile Red Drum, Sciaenops ocellatus

David, Andrew; Isley, J.; Grimes, Churchill

Most red drum Sciaenops ocellatus, age and growth research has utilized sagittal otoliths. We evaluated the other otoliths. the lapilli and asterisci. as well as the sagittae, as ageingstructures and length-at-age estimators in hatchery-reared and wild juveniles(<50 mm SL). Our otolith mounting and sectioning protocol for preparing sagittal sections required significantly less processing time with no loss in accuracy than the more traditional transverse sectioning reported in the literature. Increments in asterisci were clearly visible from the primordium to the otolith margin, whereas the nuclear region of sagittae and lapilli were more opaque and prevented detection of all rings. Asterisci were not present at hatching, but on average form six days later, therefore the addition of a constant (6 days) to the ring counts of asterisci resulted in this otolith providing more accurate ages than sagittae or lapilli. According to coefficients of determination (r2 ) generated from the relation between fish length and otolith diameter, the sagitta, asteriscus, and lapillus predict fish length in descending order. However, because inner rings on sagittae were usually undetectable, lengths at ages cannot accurately be predicted. All rings are observable in the asteriscus; thus, by using the 6-day adjustment factor accurate length-at-age prediction is possible.

Differences Between the Sagitta, Lapillus, and Asteriscus in Estimating Age and Growth in Juvenile Red Drum, Sciaenops ocellatus

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