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Vol. 53, 2014
Occurrence and biological characteristics of glass eels of
the Japanese eel Anguilla japonica at the Cagayan River of
Luzon Island, Philippines in 2009
Tatsuki
Yoshinaga1*, Jun Aoyama2, Akira Shinoda3, Shun Watanabe2,5, Rhodora V
Azanza4 and Katsumi Tsukamoto2,5
1School of Marine Biosciences, Kitasato University, Kanagawa 252-0373, Japan
2Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan
3Department of Biology, Tokyo Medical University, Tokyo 160-8402, Japan
4The Marine Science Institute, University of the Philippines, Quezon City 1101, Philippines
5Present address: College of Bioresource Sciences, Nihon University, Kanagawa 252-0880, Japan
Abstract
Background: 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.
Results: 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.
Conclusions: 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.
Key words: Anguilla
japonica; Cagayan River;
Japanese eel; Philippines.
*Correspondence: E-mail: yosinaga@kitasato-u.ac.jp
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