Abstract
The Japanese eel Anguilla japonica spawns in the North Equatorial Current in the Philippine Sea and their larvae are transported to their freshwater growth habitats in East Asia. Here we report the occurrence and biological characteristics of glass eels of A. japonica that were collected on northern Luzon Island of the Philippines, the southern limit of the distribution range of this species. Anguillid glass eels recruiting to the Cagayan River estuary in January and February 2009 were collected and identified using their morphological and genetic characteristics. Among the 767 specimens, 52 glass eels collected in January were found to be A. japonica, while the remaining were tropical anguillid species. Age estimation revealed that the glass eels of A. japonica from northern Luzon Island were 147.2 ± 21.3 days old (mean ± sd) with a range between 111 and 185. The hatch dates of these A. japonica suggested that they were derived from at least four spawning events in the 2008 spawning season. Despite the increasing demand on the glass eels for aquaculture in the area where the five anguillid species simultaneously recruit, abundance of each species is yet unknown and investigations will be important for the protection of stock of the anguillids.
Highlights
The Japanese eel Anguilla japonica spawns in the North Equatorial Current in the Philippine Sea and their larvae are transported to their freshwater growth habitats in East Asia
The A. celebesensis specimens that were previously reported from the Cagayan River were likely erroneously identified as that species due to their morphological similarity with A. luzonensis that was not known to exist at that time (Tabeta et al 1976; Watanabe et al 2009), but the total number of anguillid species recruiting to the northern Luzon Island has not yet been investigated enough
The short-fin specimens were considered to be A. bicolor pacifica because it is the only short-finned eel ever observed in the Cagayan River (Tabeta et al 1976) or that is present in the western North Pacific (Ege 1939; Watanabe 2003)
Summary
The Japanese eel Anguilla japonica spawns in the North Equatorial Current in the Philippine Sea and their larvae are transported to their freshwater growth habitats in East Asia. We report the occurrence and biological characteristics of glass eels of A. japonica that were collected on northern Luzon Island of the Philippines, the southern limit of the distribution range of this species. The Japanese eel Anguilla japonica has been one of the most valuable fishery resources in East Asian countries. The aquaculture of these eels solely depends on the glass eels harvested in estuaries because the artificial production techniques for anguillid eels have not yet been established at a commercial scale.
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