Validation of Daily Growth Increment Deposition in Sagittal Otoliths of the Young of the Year Lithognathus mormyrus

Abstract

This paper aims to validate the micro increment deposition in the sagittal otoliths of young of the year (YOY) Lithognathus mormyrus in the shallow waters of Çanakkale, Turkey. Wild YOY specimens of L. mormyrus were captured and reared to validate the daily micro increment formation in sagittal otoliths. The formation of daily sagittal micro increments was validated using by alizarin Red S (ARS), at a concentration of 0 (control), 50 mg/lt, 100 mg/lt, 150 mg/lt, 200 mg/lt and 300 mg/lt. The natural photoperiod was applied, and no food was given throughout the marking period. The tanks kept strongly aerated to maintain the pH ~ 7. YOY fish were kept in different aquariums for 17 days post-dyeing and then re-dyeing as before and kept alive for a further 20 days. ARS marks were clearly observed in 71.7% of the YOY L. mormyrus sagittal otoliths under a fluorescent microscope. However, no mark could be observed in any of the samples of 50 mg/lt ARS treatment. Chi² tests revealed that the linear regressions of the number of micro increments between ARS marks against number of elapsed times was not statistically significant. This result showed that micro increment deposition on the sagitta were laid down daily under the experimental conditions and can be used to detect the daily age information for YOY L. mormyrus.