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Notes: Abstract The lipid composition of tropical marine reef fishes is poorly known, despite their use as food by local human populations and recent interest in health-related benefits of fish lipids. We examined the composition of lipids from epaxial muscle, liver, and two storage sites [mesenteries surrounding the gut (intraperitoneal fat, IPFs) and retroperitoneal fat bodies (FBs) posterior to the peritoneal cavity] in three species of surgeonfishes from Ishigaki Island, Japan: Naso lituratus (Bloch and Schneider, 1801), Acanthurus lineatus (Linnaeus, 1758), and A. bariene (Lesson, 1830). Triacylglycerols dominated all samples of neutral lipid and constituted ≥ 99% of FBs and IPFs. Polar lipids generally contained large fractions of phosphatidylethanolamine and phosphatidylcholine. Quantified fatty acids ranged in length from C14 to C24. C16 fatty acids prevailed (〉35% of neutral fatty acids, 〉23% of polar fatty acids), although C18 (〉16 and 〉14%, respectively) and C20 acids (〉8 and 〉19%, respectively) were also common. Saturated fatty acids, dominated by palmitic acid (16:0), comprised 38.7 to 50.7% of acids from neutral lipids and 30.8 to 41.1% from polar lipids. The most common monounsaturated acids were 18:1n9 and 20:1n9. Polyunsaturated acids were prevalent in polar lipids (especially 20:4n6, 20:5n3, 22:2n3, 22:5n3, 22:5n6 and 22:6n3). Common polyunsaturated acids of neutral lipids were 18:2n6, 18:4n3, several n-3 and n-6 C20 acids, 22:2n3 and 22:5n3. IPF and FB were almost identical across species, and lipids of fat bodies (IPFs, FBs) were more similar to those of muscle than those of liver for all three species. The FBs appear to constitute an accessory storage site, which overcomes constraints on lipid storage imposed by a small, inflexible abdominal cavity that contains both viscera and consistently voluminous gut contents. Fatty acid signatures indicate that largely overlooked epiphytic or epilithic diatoms contribute significantly to lipid acquisition. The combination of large quantities of both saturated and n-3 and other polyunsaturated fatty acids in surgeonfishes, in contrast to low saturates and high polyunsaturated acids in lipids of commercially important cool-water fishes, suggests that a study of dietary effects of fish lipids on human inhabitants of the tropics may be instructive insofar as human health and nutrition are concerned.

Notes: Hatchery-reared juvenile black sea bream Acanthopagrus schlegeli (Bleeker) are characterized by high lipid storage and low levels of highly unsaturated fatty acids in their bodies. In the present study, we assessed the effects of dietary fortification of the diet with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on the improvement of physiological activity. Black sea bream 50 days old with an average weight of 0.02 g were reared for 50 days on either a control diet (commercial diet) or a commercial diet fortified with 3% EPA and DHA. The fortification with EPA and DHA reduced lipid storage in adipocytes in the intraperitoneal cavity, but decreased muscle lipid level. Consequently, the total lipid level decreased in the bodies of the fish. The proportions of EPA and DHA in muscle, liver and adipocytes were markedly increased by diet fortification, and the EPA and DHA proportions did not differ from those of wild fish. The cell diameter of adipocytes was reduced by EPA and DHA fortification. Liver function and resistance to air-dipping were improved by fortification. The results of a starvation test revealed the efficient mobilization of lipid reserves in response to energy demands prior to protein exhaustion in the EPA/DHA-enriched group. The results implied that increasing the incorporation of dietary EPA and/or DHA should be considered in the larval stage of black sea bream culture.

Notes: As the fact that feeding Spirulina can improve carcass uality of fish, this study describes the effect on muscle protein in red sea bream, Pagrus major. The fish were fed on a diet supplemented with 2%Spirulina for 95 days under commercial rearing conditions. Spirulina feeding elevated protein synthesis, which was estimated by muscle RNA/DNA and RNA/protein ratios. Muscle protein was fractionated into sarcoplasmic, myofibrillar, alkali-soluble and stromal fractions. The stromal fraction was significantly higher in the Spirulina- fed group. The proportion of the fractions approached that of wild fish somewhat by Spirulina- feeding. The results possibly indicate that Spirulina contributes to elevate protein assimilation and increase stromal fraction.

Notes: To examine the possibility of dietary α-starch in reducing feed costs in a practical diet, α-starch was supplemented at 10, 20, 30 and 40% in a composed diet having the same protein level. The four diets were fed to ayu, Plecoglossus altivelis (initial weight 9.1 g) for 43 days. Growth and feed efficiency increased with the supplement, with values highest in the 30–40%α-starch diet. The level of dietary α-starch did not affect the proximate muscle composition; although the hepatosomatic index was not affected, liver glycogen increased with increasing dietary α-starch. The dietary α-starch did not influence evacuation time from the gut, and was well digested through passage in the gut, mainly between the stomach and the anterior part of the intestine. Ayu have an ability to adapt their metabolism to high dietary α-starch, and can digest 40% or more in a composed diet. Although the muscle lipid content did not change, the fatty acid composition was influenced by dietary starch. With the elevation of dietary starch, a decrease of C18:2n-6 and an increase of C22:6n-3 occurred. These results indicate that at least 40%α-starch can be used in practical diets for ayu.