The first time of leptocephali of Japanese eel Anguilla japonica collected by Taiwanese researchers

Abstract

Three leptocephali of Japanese eel Anguilla japonica were collected in the presumed spawning ground of 12"30'-14"30'N and 131"30'-140"30'E, on 16 to 23 August, 1995. It was the first time of such collection by Taiwanese researchers. Total lengths of the Ieptocephali were measured as 27.4, 28.8 and 31.4 mm, respectively. Their daily ages were estimated to be 46, 50 and 51 days by counting otolith growth increments, and growth rates be 0.577-0.658 mm.d^-1. The daily ages of these three leptocephali were back-calculated for birth dates be July 1 and 3, and the spawning dates were on June 2 and 4 of the lunar calendar which were in the period of new moon. This study confirms that Japanese eel spawns in summer. Based on the localities of collections and the westward direction of ocean current, the body lengths and the daily ages of these three leptocephali are difficult to depict the spawning ground as previously known. Spawning ground is probably rather widely spread.