International eel symposium, 2003 - Quebec August 11, 2003
Poster Session

Early Growth History of Anguilla japonica Determined from Otolith Microstructure in Glass Eels

Lee, T.W.* Department of Oceanography, Chungnam National University, Taejon 305-764, Korea twlee@cnu.ac.kr
Moon, H.T. Department of Oceanography, Chungnam National University, Taejon 305-764, Korea
Kim, G.-C. Fisheries Oceanography and Zooplankton Ecology Research Lab., School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055 STN CSC, Victoria, BC, V8W 3P6

Presenter email address: twlee AT cnu.ac.kr

Abstract Text: The early growth history of eel Anguilla japonica. was determined by examining the otolith microstructure of glass eels collected from the three Korean estuaries from January to May in 1998. The mean total length (57.1+/-2.09 mm, mean+/-SD) and the mean daily growth increments in otoliths of glass eels (188+/-9.6 d ) did not show the significant geographic and temporal differences. The discrepancy between the back-calculated spawning times from glass eels otoliths and leptocephalus otoliths implies that glass eels otoliths may stop growing during their migration over the continental shelf. Glass eel otoliths consist of an inner transluscent zone formed during the leptocephalus stage and an outer opaque zone formed during metamorphosis. The mean age at the onset of metamorphosis was estimated to be 129+/-7.1 d, and the mean duration of the metamorphic stage was estimated to be 45+/-5.0 d. On average, 15+/-5.1 growth increments was observed outside the metamorphic zone. We considered that the otoliths stop growing after the glass eels migrated over continental shelf at the temperature below 13.5 ^oC. The mean total length at the onset of metamorphosis was estimated to be 51.7+/-3.44 mm using the relationship between total length and otolith rardius of leptocephail