Otolith Daily Increments in the Japanese Eel

Abstract

In order to validate the otolith increments of the Japanese eel Anguilla japonica time mark was incorporated in the otoliths of elvers by immersing in tetracycline (TC) solution. They were reared for 40 days afterwards, and the otolith increments expressed in number of circuli outside the TC fluorescent mark were examined.
The number of increments between TC mark and sagittal otolith edge was 38.6±2.9 (mean±SD), N=41, and roughly coincided with the number of days after TC treatment till the sacrifice, suggesting the daily deposition of the increments in sagittae of the Japanese eel. It was concluded that the otolith increment was applicable for the age determination of elver of the Japanese eel.