Calcein as a Fluorescent Marker of Otoliths of Larval and Juvenile Fish

Abstract

Calcein is a fluorescent compound that can bind with alkaline earth metals, such as calcium. Upon binding, an increase in fluorescence under ultraviolet light results. Therefore, calcein was evaluated as potentially useful for creating a fluorescent mark in the otoliths of larval and juvenile fish. Such a mark was produced in the sagittae of larvae and juveniles of three species of estuarine fishes after a 2-h immersion in a solution of 125 mg/L in seawater. The mark was easily distinguished under ultraviolet epifluorescent microscopy. This technique provides an alternative to the use of tetracycline in age and growth studies.