Genetic identification of Conger myriaster leptocephali in East China Sea

A subsample of Conger leptocephali collected in the East China Sea (ECS) was genetically analyzed and most were found to be the larvae of Conger myriaster, the most commercially important marine eel species in East Asia. However, these leptocephali (22.3-74.0 mm total length [TL]) did not have a complete row of lateral pigmentation, like the leptocephali of this species are commonly known to have when they are collected over the continental shelf or in coastal waters as they recruit. These leptocephali were in the western edge of the Kuroshio Current and the mixing zone over the shelf in the northern part of the ECS, and two smaller leptocephali (22.3, 46.5 mm TL) were collected to the south of the Ryukyu Islands. This evidence of an ontogenetic change in the presence of lateral pigmentation of C. myriaster indicates that previous efforts to determine the spawning area and recruitment patterns based on only morphological examination of Conger leptocephali in the region must be reconsidered. New research efforts based on genetic identification methods are needed to understand the spawning ecology and recruitment of this important fishery species.