Progression in artificial seedling production of Japanese eel Anguilla japonica

Hideki Tanaka

doi:10.1007/s12562-014-0821-z

Abstract

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.

Highlights

It is said that the Japanese consume around 40,000 tons of eel every year
More than 99 % are farmed eels reared from fry known as glass eels, which are caught in the wild
Full-life cycle culture from egg to adult is possible in many fish species, it has never been successfully accomplished in eels, despite arduous efforts for many years

Summary

Introduction

It is said that the Japanese consume around 40,000 tons of eel every year. More than 99 % are farmed eels reared from fry known as glass eels, which are caught in the wild. Since the end of the 1980s, the author and others at the National Research Institute of Aquaculture (NRIA) of the Fisheries Research Agency (FRA) have been attempting to improve technologies for maturity inducement in parental eels and artificial insemination, based on many achievements by previous researchers [5,6,7] This has realized the production of hatched larvae of rather good quality, in fairly large volume and on a systematic basis [8, 9]. Most researchers connected with eel research in Japan, including those at the FRA and prefectural fisheries research institutes, universities, etc., have joined forces in tackling challenges in the technological development of cultivation and maturation of parental eels, feed for larvae, and optimization of the rearing environment All these efforts culminated in successful rearing of artificially hatched eels, linked to the production of the generation, whereupon “full-life cycle culture” was achieved in the spring of 2010. The author introduces the research progression of artificial seedling production of the Japanese eel, with particular emphasis on a key challenge: the development of larval rearing technology

Information gleaned from research on life history

Findings

History of research on artificial seedling production