DOI: 10.26650/ase.2026.1925630 ISSN: 2602-473X

Effectiveness of Alizarin Red S Immersion for Validating Otolith Daily Growth Increments in Juvenile Sharpsnout Seabream (Diplodus puntazzo)

Hakan Ayyıldız, Pınar Çelik, Aytaç Altın
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This study validates daily increment formation in otoliths of juvenile sharpsnout seabream (Diplodus puntazzo) from the Dardanelles using Alizarin Red S (ARS) marking at four concentrations (50, 100, 150, and 200 mg/L). Eighty wild-caught juveniles (20–76 mm total length) were subjected to 24-hour ARS immersion, followed by 10 days of captivity. Mortality varied among treatments, with cumulative rates of 5.9–12.5% across ARS groups and 6.7% in the control, with the highest mortality occurring in the 100 and 200 mg/L groups (12.5% each). ARS marks were successfully detected in 75.3% of examined otoliths, with mark quality increasing at higher concentrations. Chi-square analysis comparing increment counts between the ARS mark and otolith edge with elapsed time revealed no significant difference (χ² = 0.355, df = 55, P = 0.93), confirming daily periodicity of increment formation. Based on the balance between marking success and fish survival, 50–100 mg/L represents an optimal concentration range for future studies. These findings provide robust validation for daily age estimation in juvenile D. puntazzo from the Dardanelles, supporting age-based growth studies and fisheries management in this ecologically important region.

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