Program and Abstracts(PDF)

Presentation 10
SUCCESS OF ARTIFICIAL COMPLETION OF THE JAPANESE EEL (Anguilla
japonica) LIFE CYCLE
Hitoshi Imaizumi* 1 , Yoshitsugu Masuda 1 , Hiroshi Hashimoto 1 , Kentaro Oda 1 , Junichi Adachi 2 ,
Syunji Kaji 3 , Kazuhisa Teruya 4 and Hideki Tanaka 5
1 Sibushi Station, National Center for Stock Enhancement, Fisheries Research Agency
2 Public Relations Section, Headquarters, Fisheries Research Agency
3
Minamiizu Station, National Center for Stock Enhancement, Fisheries Research Agency
4 Yaeyama Station, Stock Enhancement Technology Section, Seikai National Fisheries Research
Institute, Fisheries Research Agency
5 National Research Institute of Aquaculture, National Fisheries Research Institute, Fisheries
Research Agency
*Email: imaizumi at affrc.go.jp
Eel farming is dependent on the natural resources of glass eels. The catches have recently
declined, destabilizing the business of eel farming. For that reason, there is an urgent need to
achieve the production of juveniles in a hatchery, eliminating dependence on natural resources.
However, most of the life cycle of eels has remained unknown. Consequently, there is little
knowledge related to the course of maturing and spawning or to the habitat and food in the larvae
period, making it necessary to use the process of trial and error in various studies. First, because
eels do not mature or spawn under culture conditions, artificial maturation using hormone
administration has been developed, which has made fertilized eggs available; the development of
techniques for the culture of larvae was started. However, that development was extremely
difficult because the culture was not possible merely by the application of existing culture
methods other fish. About 30 years after the first hatchlings were obtained; culture up to the stage
of glass eels was finally achieved via the discovery of a feed composition available for hatchlings
and the development of a feeding method that uses the behavior characteristics of hatchlings.
National Center for Stock Enhancement, Fisheries Research Agency, has been engaged in the
mass production of glass eels through improvement of artificial maturing and culture methods,
aiming at complete life cycle culture by checking the fertility of hatchery-reared eels with an eye
to technical development of breeding that engenders the rearing of parent eels and mass
production without depending on wild eels. Shibushi Station prepared 26 hatchery-reared eels in
all, including 10 females (313 g mean body weight) and 16 males and sex-unknown individuals
(384 g mean body weight), which were artificially hatched hatchlings obtained in 2004–2006.
They developed to glass eels and were reared for an additional 4–6 years after being subjected to
artificial maturing. Results show that 2,150,000 eggs in all were collected from 9 of 10 females.
The fertilized eggs were obtained through artificial insemination. The mean fertility was 65.9%,
the mean hatchability was 37.0%, and the mean survival rate at 6 days after hatching was 34.8%.
These results of maturing and egg yield were better than those for wild eels in captivity. This
study proved that hatchery-born eels can produce artificially hatched larvae of a second
generation, achieving complete life cycle culture for the first time in the world. We hope that
further research will engender the development of breeding techniques that provide mass
production of glass eels as well as development of maturation and egg collection methods
without dependence on natural resources.
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