Contrasting assemblages of leptocephali in the western Pacific

To learn about the larval distributions and reproductive ecologies of marine and freshwater eels, the assemblages of anguilliform leptocephali were compared between 2 ecologically different areas along the margins of the western Pacific Ocean using the catch data from 2 sampling surveys targeting leptocephali. The assemblages on the outer shelf and slope of the East China Sea in November and December 2000 were dominated by the leptocephali of 2 abundant taxa of congrid and synaphobranchid eels that had been spawning along the shelf break, and by the leptocephali of 3 other families. The leptocephali of many other families were rare, and catch rates were lower over deeper water to the south. In contrast, assemblages of leptocephali were very diverse and showed a widespread presence of most families over the deep water in close proximity to Sulawesi Island in the Indonesian Seas in May 2001, but there were no high catch rates due to the lack of recent spawning activity offshore. As a result, the northern study area had a higher overall catch rate of leptocephali, but much lower richness, diversity, and evenness of taxa than the southern study area in the Indonesian Seas. Cluster analysis distinguished 3 general assemblages that corresponded mostly to each of the 2 study areas and to a group of stations that were mixed between the 2 study areas. This analysis indicates that assemblages of leptocephali can vary widely depending on the location of sampling and on the eel fauna in each particular area.