Program and Abstracts(PDF)

Satellite symposium 1
ARTIFITIAL COMPLETION OF THE JAPANESE EEL, ANGUILLA JAPONICA,
LIFE CYCLE: CHALLENGE TO MASS PRODUCTION
Yoshitsugu Masuda 1* , Hitoshi Imaizumi 1 , Kentaro Oda 1 , Hiroshi Hashimoto 1 , Hironori
Usuki 1 , and Kazuhisa Teruya 2
1 Shibushi Station, National Center for Stock Enhancement, Fisheries Research Agency,
Shibushi, Kagoshima 899-7101, Japan
2 Stock Enhancement Technology Section, Ishigaki Tropical Station, Seikai National Fisheries
Research Institute, Fisheries Research Agency, Ishigaki, Okinawa 907-0451, Japan
* Email: masuday at affrc.go.jp
Development and modification of slurry type diets made from shark-egg powder have enabled
glass eel production in captivity by the group of Dr. Tanaka in National Research Institute of
Aquaculture 1-3) . Based on this success, recent investigations have specifically examined
establishment of techniques for consistent mass production of glass eels. Now, there are many
problems to settle in rearing eel larva, leptocephalus. The current procedures of feeding and
maintenance are too troublesome for application to mass rearing. In addition, rearing period is
too long and can not be correctly estimated. Moreover, limited supply of diet material,
shark-egg, cannot meet mass production of glass eels. To overcome these problems, we
suggested colloid-type diet and try to develop automatic system of rearing procedures. We
also try to develop the diets made from new materials besides shark-egg. Then we succeeded
shortening the rearing period from egg to glass eels. In our presentation, we would introduce
these challenges to achieve mass production.
Annotated Bibliography of Key Works
1) Tanaka, H., H. Kagawa, and H. Ohta. 2001. Production of leptocephali of Japasese eel,
Anguilla japonica, in captivity. Aquaculture 201. 51-60.
Despite intensive research on wild and captive eels, no resource has so far provided access to
all life cycle stages of the Japanese eel Anguilla japonica. The transition from the
preleptocephalus, newly hatched larva, to the leptocephalus stage, typical leaf-like eel larva,
has, therefore, remained the missing link in the eel life cycle. We recently found that a
slurry-type dit made from shark egg powder is suitable feed for captive-bred eel larvae. The
larvae were successfully reared with this diet in aquaria for 100 days and raised to 22.8 mm in
total length, TL. Age, RL, and body proportions of the reared specimens overlapped with
those of wild leptocephali. We revealed for the first time the transition from the
preleptocephalus to the leptocephalus stage of the eel.
2) Tanaka, H., H. Kagawa, H. Ohta, T Unuma, and K. Nomura. 2003. The first production of
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