Progression in artificial seedling production of Japanese eel Anguilla japonica

Eel aquaculture, though thriving nowadays, is totally dependent on the successful capture of wild eel fry and glass eels for its seedlings. The declination of eel resources in recent years has resulted in an urgent need for technology development in artificial seedlings production on an aquaculture basis, in order to protect natural resources and to stabilize the eel supply in the farming industry. Since the life history of the eel holds many mysteries, artificial hatching and rearing of larvae has long been regarded as an extremely difficult task. However, in recent years, the spawning ground of the Japanese eel has finally been located after continuous effort with intensive marine surveys, in which wild parental eels were captured, followed by the collection of fertilized eggs and the harvest of newly hatched preleptocephali. Meanwhile, through the collaborative efforts of many researchers, progress has also been made in improving technologies for artificial maturation of parental eels, which do not mature naturally in captivity, as well as in the technology for artificial hatching. Moreover, a technology for producing feed-rearing eel hatchlings, the most challenging process of all, has advanced rapidly after suitable feed was developed in the 1990s. Then, in 2002, for the first time in the world, larvae were successfully reared up to the glass eel stage, and second generation artificial hatchlings were born in 2010. In this way, eel farming technology that is not reliant on natural resources has been developed. There are strong hopes now for a technology for stable mass production of glass eels to be developed in the near future.