Validation of Daily Growth Increments in Otoliths of Milkfish Larvae by Oxytetracycline Labeling

The formation of growth increments in the otoliths of wild-captured larvae of milkfish Chanos chanoswas validated by the oxytetracycline-labeling method. Immersion of the fish in 400–500 mg oxytetracycline/L for 24 h is recommended for marking the otoliths of milkfish larvae. A golden-yellow band and the newly deposited growth increments in the otolith were both discernible after marking. Otolith growth increments were deposited at the rate of about one per day, and their formation rate was unaffected by the growth rate of the fish. However, increment width varied with the growth rate of fish. Therefore, otolith growth increments are a valid characteristic for determining daily age and for studying the growth history of wild milkfish larvae.