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Artificial Japanese Glass (Anguilla japonica) Production in the mature stage between 10 and 20 years. Marine habitat, Abstract but commences in freshwater. Freshwater are very valuable fish species, principally in Asian and European countries. Over 97% of worldwide eel Japanese eel, Anguilla japonica, is a very important cultured production is based on farming of the , Anguilla species in East Asia due to its high market value, desirable anguilla and the Japanese eel, Anguilla japonica. Eel farming taste and recent supply shortage (Ren et al., 2007). Five major is a capture-based activity. It is based on the producers of this species are , Japan, Korea, Malaysia practice of collecting juvenile eels from the wild and on- and Taiwan. The eel aquaculture industry in these countries growing in captivity to marketable size using aquaculture has been growing, e.g. in Korea its production increased from techniques. Due to their complex life cycle, research efforts 2739 tons in 2000 to 6766 tons in 2009 (Son et al., 2011). Eel have not yet managed to produce glass eels on a commercial culture has depended on natural captured Japanese glass scale. After a series of efforts, Korea made a breakthrough by eels, and the highest amount of fishing reached 160 tons (15 producing two Japanese glass eels in 2012. Several other tons in Korea) in East Asia in 2006. Recently, the amount of phenomenal pieces of research were conducted to produce Japanese glass eel fishing has been gradually decreased and the artificial Japanese glass eel, as well as to develop the the value reached 15 tons (one ton in Korea) in East Asia, complete package for eel aquaculture in Korea. 2013. Environmental variation, overfishing, climatic changes, pollution and infections with the swim bladder parasite Introduction () and/or eel viruses have been The family , commonly referred to as freshwater implicated as causes for the current decline in the Japanese fish, is composed of at 16 species and three subspecies, all in glass eel population (Tsukamoto, 2009). the genus Anguilla (Tsukamoto, 2009). Anguilla species are distributed throughout tropical and temperate waters, expect for the Eastern Pacific and South Atlantic (Aoyama et al., 1999). The various life stages of all Anguilla species are harvested and traded on a global scale for farming and consumption. As catadromous fish, they migrate from rivers and inland bodies of water to the oceans to breed, and then the young return to freshwater. For all Anguilla species, the life cycle is essentially the same (Fig. 1).

The limited and inconsistent availability of wild broodstock Japanese eel, as well as early survival rate decreasing in culture of the tropical Japanese glass eel (Luo et al., 2013) and the protection or import regulation of Japanese glass eel resources (Crook et al., 2013) over the last decades, increased the requirement for artificial eel production in captivity. Artificial eel production has been studied since the 1960s, : The oceanic pelagic larval eel, which migrates and Yamamoto and Yamauchi first succeeded in producing from the spawning area to the continental shelf. Narrow, Japanese eel larvae in 1974 from eggs obtained from deep-bodied, shaped like a willow leaf. Glass eel: Small, hormone-treated eels, and Yamauchi et al. (1976) succeeded transparent juvenile eel formed by metamorphosis of in rearing pre-leptocephalus for two weeks. In 2002, the leptocephalus. Metamorphisis occurs at sea, perhaps near the National Research Foundation of Korea (Korea Research edge of the continental shelf. They are not fully pigmented Foundation) approved the national project on “NRF-2002- juveniles. Marine and estuarine habitat. Elvers: Fully 005-F00002” through the Feeds and Foods Nutrition Research pigmented juvenile eel, with a total length under 30 cm and Center (FFNRC) as the priority research institute at Pukyong less than five years old. Predominantly freshwater habitat. National University, Busan, Korea. This project was the first Yellow eel: Eel residing in continental waters, with a size official Korean Government Support Project almost from generally over 30 cm long and more than five years of age. 2002 to 2004. FFNRC successfully produced the artificially This stage typically lasts several years. Predominantly matured male and female broodstock Japanese eel and freshwater habitat. Silver eel: A sexually maturing eel, fertilised eggs in 2003. This research fund was terminated in migrating to the oceanic spawning area. They usually reach 2004, and the National Fisheries Research and Development Institute (NFRDI) continued this research in 2006 with fund

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research from FFNRC, successfully hatching two Japanese glass eels in 2012. Artificial production technology of Japanese eels has improved markedly in Korea, and further studies are necessary to obtain high quality and mass production of Japanese eel eggs. Additionally, artificial reproduction of the European eel, Anguilla anguilla (Palstra et al., 2005), the New Zealand longfin eel, Anguilla dieffenbachia and the shortfin eel, Anguilla australis (Lockman and Young, 2000) have been attempted with a number of research groups.

Research on Japanese eel reproduction is complicated, because broodstock eels stop feeding when silvering in nature. For example, Chow et al. (2010) found that Japanese eels caught in the spawning area had not been eating in the marine phase of the migration. Also in captivity, feeding is terminated after transfer to saltwater prior to induction of maturation. Moreover, it is also clear that the availability of an optimal diet is identified as a crucial factor for the sexual maturation and reproduction of the Japanese eel. For Japanese eels, all the qualitative and quantitative Fig. 1. Life cycle of eel (Gissurardottir, 2006) requirements for reproduction have to be met from their body reserves, highlighting the importance of pre-spawning nutrition. Delivering more information Fix-a-Form® multi-page labels, the clever application allowing more information on your product.

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Summary of Research and Development of Japanese Eels Ginneken VJT and van den Thillart GEEJM. 2005. Artificial (A. japonica) in Korea maturation and reproduction of European silver eel: Recent nutrition studies have contributed further to a better Development of oocytes during final maturation. knowledge of the requirements of proteins, lipids, vitamins Aquaculture 249, 533-547. and additives for the maturation process in the Japanese eel. • Ren T, Koshio S, Ishikawa M, Yokoyama S, Micheal FR, It was shown that the optimum dietary protein (44.3%), P/E Uyan O and Tung HT. 2007. Influence of dietary vitamin ratio (24.1 mg protein/kJ), linolenic acid (LNA, 0.35~0.5%), C and bovine lactoferrin on blood chemistry and non- linoleic acid (LA, 0.5~0.65%), vitamin E (21.2 mg/kg), vitamin specific immune responses of Japanese eel, Anguilla C (41.1 to 43.9 mg/kg) in juvenile and (410.8 to 911.8 mg kg- japonica. Aquaculture 267, 31-37. 1) in broodstock, as well as additives such as quartz porphyry • Son MH, Kim KW, Kim KD and Kim SK. 2011. State of (0.7%), BAISM (0.5%) and propolis (0.25-0.5%) levels could aquacul¬ture management for optimal rearing of eel, be essential for maintenance of normal growth, physiological Anguilla japonica. Korean Journal of Fisheries and function and overall health. Still our knowledge on the Aquatic Science 44, 359-365. reproduction of Japanese eels remains limited. However, our • Tsukamoto K, Aoyama J and Miller MJ. 2009. Present previous studies have shown that final maturation in silver status of the Japanese eel: resources and recent research. female and male Japanese eels could be induced by weekly American Fisheries Society Symposium 58, 21-35. injections of salmon pituitary extract (SPE) and human chorionic gonadotropin (HCG), respectively. Also, our results indicated that artificial maturation by hormone treatment Dr. Erfan Shahkar, Nutritionist, Blue Aqua was successful only during the spring to summer seasons in International Pte Ltd. After finished his Master of seawater with low temperatures (10ºC). These results will Science on Fish Nutrition, Department of Natural provide valuable information for elevation of the artificial Resources Science, University of Lahijan, Iran. He maturation and reproduction coefficient in the Japanese eel. continue studied and finish his Ph.D. in the same major from Department of Marine Bio-Materials Future Perspectives: and Aquaculture, Pukyong National University, 1. Emphasis on nutrition of broodstock eels South Korea. Dr. Erfan recently join Blue Aqua International Pte 1.1. Cost-effective rearing process Ltd. on July, 2015 as Nutritionist. His expertise in Fish nutrition 2. Domesticate broodstock in captivity will help all farmers on the problem for highest benefit for the 3. Feed development for larvae Aquaculture. 4. New feed development for larvae E-mail: [email protected] 5. Rearing larvae in captivity 6. Selective breeding for better growth and survival 7. Disease prevention (e.g. vaccine development) Hyeon Ho Yun, Ph.D., Fisheries Science at 8. Conservation of eel resources in the wild Pukyong National University (PKNU). Current position, Researcher (Ph.D) at Department of Fisheries Biology/Feeds and References Foods Nutrition Research Center (FFNRC) Pukyong • Aoyama J, Mochioka N, Otake T, Ishikawa S, Kawakami Y, National University (PKNU). Castle P, Nishida M and Tsukamoto K. 1999. Distribution Email: [email protected] and dispersal of anguillid leptocephali in the western Pacific Ocean revealed by molecular analysis. Marine Ecology 188, 193-200. Dr. Rungtiwa Piamtongkam is now working • Chow S, Kurogi H, Katayama S, Ambe D, Okazaki M, as Regulatory affairs and technical support for Watanabe T, Ichikawa T, Kodama M, Aoyama J, Shinoda Blue Aqua International Pte., Ltd. after finished A, Watanabe S, Tsukamoto K, Miyazaki S, Kimura S, B.Sc. Biochemistry and M.Sc. Biotechnology from Yamada Y, Nomura K, Tanaka H, Kazeto Y, Hata K, Handa Faculty of Science, Chulalongkorn University, T, Tawa A and Mochioka N. 2010. Japanese eel, Anguilla Thailand. She continues studied and got her Ph.D. japonica do not assimilate nutrition during the oceanic in Microbial and Enzymatic Engineering from spawning migration: evidence from stable isotope INSA de Toulouse, France in 2010. Recently, she uses her skill on analysis. Marine Ecology Progress Series 402, 233-238. communication and networking to hand on news and technology to aqua-culturist via social media and supporting customer in the • Crook V and Nakamura M. 2013. Assessing supply chain industry worldwide. and market impacts of a CITES listing on Anguilla Email: [email protected] species. TRAFFIC Bulletin 25, 24-30. • Lockman PM and Young G. 2000. Induced spawning and early ontogeny of New Zealand freshwater eels (Anguilla Sungchul Charles Bai, Current position, dieffenbachia and Anguilla australis). New Zealand Undergraduate and Graduate Faculty, Pukyong Journal of Marine and Freshwater Research 34, 135-145. National University Professor/Department of • Luo M, Guan R, Li Z and Jin H. 2013. The effects of water Marine Bio-materials and Aquaculture, and temperature on the survival, feeding and growth of the Director/Feeds and Foods Nutrition Research juveniles of Anguilla marmorata and Anguilla bicolor Center (FFNRC) Busan 608-737, Korea (82-51) pacifica. Aquaculture 400-401, 61-64. 629-5916 • Palstra AP, Cohen EGH, Miemantsverdriet PRW, van E-mail: [email protected] or [email protected]

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