World Aquaculture - December 2014

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32 DECEMBER 2014 • WORLD AQUACULTURE •
(Willey et al. 2003) and striped bass Morone saxitilis (Harel et al.
2001).
The essential fatty acid requirements for optimal growth of
the Japanese eel were satisfied by n -3 and n-6 PUFA (Takeuchi
et al. 1980). Additionally, we investigated the optimum levels of
dietary n-3 or n-6 fatty acids and the availability of AA in elver and
juvenile stages of Japanese eel (Bae 2003, Bae et al. 2004).
In our experiment, the WG, FE and SGR of fish were
significantly influenced by dietary ARA level. WG and FE of fish
fed ARA0.8 and ARA1.2 diets were significantly greater than that
of fish fed ARA0.07, ARA0.22 and ARA0.43 diets; there were
no significant differences among fish fed ARA0.6, ARA0.8 and
ARA1.2 diets.
Castell et al. (1994) and Bell et al. (1995) demonstrated that
dietary ARA promotes growth of juvenile turbot and concluded
that ARA is an essential fatty acid for juvenile turbot. These studies
provided the first evidence that ARA is an essential fatty acid
for normal growth, development and survival of juvenile marine
fish. In addition, Koven et al. (2001) suggested the importance
of dietary ARA for improving resistance to handling stress in
gilthead sea bream larvae. The authors proposed that increased
prostaglandin E2 (PGE2) production in the ARA supplemented
fish was responsible for up-regulation of cortisol synthesis through
the hypothalamus-pituitary interrenal axis, resulting in improved
response to acute stress (Bell and Sargent 2003). On the other hand,
it has been reported that high levels of ARA in the diet negatively
affect growth and survival of the larvae of cod (Zheng et al. 1996),
Japanese flounder (Furuita et al. 1998) and yellowtail (Ishizaki
et al. 1998). Likewise, in our study, the best growth and feed
utilization effects were observed in the fish fed an optimum ARA
level in the diet. In the present study, the dietary arachidonic acid
(ARA) requirement for the juvenile eel, A. japonica based on WG
and SGR was 0.69-0.71 percent of the diet (Fig. 5).
Conclusion
As it is unlikely that capture fisheries production of Japanese
eel will increase further, substantial investment and multilateral
efforts are warranted to boost aquaculture production to meet the
ever-increasing demand for this species. A clear understanding
of the optimum level of macro- and micro-nutrients is imperative
to formulate nutritionally balanced and cost-effective diets for
Japanese eel. Based on a series of experiments conducted in our
laboratory with different age groups, vitamin C requirement is
equal to or greater than 41.1 mg/kg diet, vitamin E requirement
is >21.2 but <21.6 mg/kg diet and arachidonic acid requirement is
0.69-0.71 percent of the diet.
Notes
Sungchul C. Bai, Department of Marine Biomaterials &
Aquaculture, Feeds and Foods Nutrition Research Center,
Pukyong National University, Busan 608-737, Korea (Rep.)
Kumar Katya and Hyeonho Yun, Department of Marine
Biomaterials and Aquaculture, Feeds and Foods Nutrition
Research Center, Pukyong National University, Busan 608-737,
Korea (Rep.)
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