Otolith Microstructure and Ecology of the Conger Eel (Congen myriaster) Larvae Collected in the Seto Inland Sea, Japan

Otolith microstructure of the conger eel (Conger myriaster) larvae was observed using the scanning electron microscope with reference to the ecology in the Seto Inland Sea, Japan. The radii and the number of rings of the otoliths from the developing stage larvae were 104–145 μm and 123–172, respectively, while those from the metamorphic stage larvae were 140–496 μm and 159–212, respectively. The number of rings correlated highly with the radius of otoliths (r—0.905). The growth of radius and increase of number of rings were recognized for the first time in the otolith of the conger eel larvae in relation to growth of the head during the metamorphic stage. It was assumed that narrow and clear rings in the range from the first to about the 140th-150th ring correspond to the period from hatching to developing stage of leptocephalus, while wide rings in the range from about the 150th ring to the otolith margin corresponed to the period from the latest developing stage to the metamorphic stage. The daily growth rhythm in the otolith could not be proved from reared larvae due to the disturbance of ring arrangement in the marginal region.