Validation of otolith daily increments in the tropical eel Anguilla marmorata

To determine the periodicity of the deposition of growth increments in the otolith of the glass eels of the tropical eel Anguilla marmorata, an otolit h validation experiment was performed. Glass eels were captured at the mout h of the Poigar River, north Sulawesi Island, Indonesia, and then immersed in an alizarin complexone (ALC) solution to mark their otoliths. After bein g held under natural conditions in the river for 20 d, it was found that th e number of rings outside the ALC mark was 20.1 +/- 0.7 (mean +/- SD), whic h coincided with the number of days after the ALC treatment. This validatio n experiment indicated that the growth increments in the otoliths of A, mar morata glass eels were deposited daily and can be used for daily age determ ination.