Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment

Essential Fatty Acid Requirement of the Chinese Mitten Crab

Xiao-bo Wen, Li-qiao Chen, Chun-xiang Ai, Zhong-liang Zhou, Hongbo Jiang


Lipids are important nutrients for the growth of crustaceans, not only as energy sources but also as essential nutrients such as sterols, essential fatty acids (EFAs), and phospholipids (Kanazawa et al. 1985). Some combination of n-3 fatty acids, n-6 fatty acids, or both are required in all animal diets, including those of important cultured fish and prawn species (Castell et al. 1972; Kanazawa and Teshima 1977,1979; Kanazawa et al. 1978; Watanabe 1982; Watanabe et al. 1989; Sargent et al. 1990; Tskeuchi et al. 1990). Results of studies on the nutritional requirements of marine fish and prawns have shown that fatty acids of the n-3 family have greater EFA value for these species than fatty acids of the n-6 family (Kanazawa et al. 1979; Castell 1981; Watanabe 1982; Xu et al. 1993).

Results of studies on EFA requirements indicate that the nutritional value of lipids for marine crustaceans is also a function of the type of unsaturated fatty acids that they contain and their degree of unsaturation. Kanazawa and Teshima (1979) demonstrated that unlike rainbow trout Oncorhynchus mykiss, several species of marine crustaceans exhibit only limited ability to elongate and desaturate 18-carbon polyunsaturated fatty acids (PUFAs) of the n-3 and n-6 series to the longer-chain, more highly unsaturated forms. In studies with Japanese prawn Penaeus japonicus (Kanazawa and Teshima 1977), Indian white prawn P. indicus (Read 1981), and common prawn Palaemon serratus (Martin 1980), 18:3n-3 has greater EFA value than 18:2n-6. In Japanese prawn, longer-chain n-3 highly unsaturated fatty acids (HUFAs) such as eicosapentaenoic acid (20:5n-3, EPA) (Kanazawa et al. 1978) and docosahexaenoic (22:6n-3, DHA) (Kanazawa and Teshima 1979) had greater EFA value than 18:2n-6 or 18:3n-3. In a preliminary study with fleshy shrimp Penaeus chinensis, the order of nutritional value of the purified fatty acids (when added individually at 1% of the diet) was 22:6n-3 > 20:4n-6 > 18:3n-3 > 18:2n-6 (Xu et al. 1993, 1994). Studies with Japanese prawn had shown that the prawn required linoleic and linolenic acids as well as EPA and DHA as EFAs, and their nutritional values increase in this same order (Guary et al. 1976; Kanazawa et al. 1977, 1978).

The Chinese mitten crab Eriocheir sinensis is considered to be a good crustacean species for culture in China. In recent years, significant advances have been made in this industry, progressing from extensive to intensive culture. Therefore, production has increased rapidly. For intensive culture, the use of formulated diets is essential. In crustaceans, the nutritional requirements of Japanese prawn had been determined through the use of semipurified test diets (Deshimaru and Shigeno 1972; Deshimaru and Kuroki 1975; Deshimaru and Yone 1978a, 1978b, 1978c; Kanazawa 1985). However, limited information is available about the nutritional requirements of Chinese mitten crab. Some information has been reported for this species about optimal dietary protein levels and sources (Chen et al. 1994) but not about optimal EFA levels.

The objectives of this study were to determine the dietary EFA requirements of Chinese mitten crab and to evaluate the relative nutritional values of these fatty acids.