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Daily increments in the sagittal otoliths of young nagroor, Pomadasys kaakan (Family: Haemulidae) were investigated using alizarin complexone (ALZ). Counts between annual marks and marginal increment analysis of adult wild fish were used to validate the annuli and time of their formation. Young nagroor deposited daily otolith increments under laboratory conditions at 17–20°C. Compared to cultured fish, the daily increments of wild fish were relatively easy to discern and count. The annulus was composed of striated aggregations all round the otolith’s thin transverse sections. The average daily increment counts between the annuli were 266, 326 and 276 for the first 3 years, respectively; however, this method is unsuitable for validation of the second and later annuli due to a lower increment number than expected of 365 increments. The recent annuli formed on the otolith edge were observed in most of the March–May otolith samples. All data of marginal increment of otoliths were pooled for the years 1992–1995, which indicated that the peak formation of annuli was during March–June. The data also indicate that juvenile and immature fish (14–22 cm total length) form the first annulus before the onset of ovarian maturation. |
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