天然および養殖アユの脂肪酸組成について

Abstract

Differences of lipids, especially fatty acid compositions between wild and cultivated sweet smelt were studied, since fundamental data concerning about lipids of the fish were not available, though production of the fed “Ayu” has been increasing year after year. A group of infant fish was released to a stream (River Chikuma) middle of May-though it was a little later in season than an average year-1963, another group was cultivated at a fish pond in the area. After three months samples (Table 1) were caught and such several parts as dorsal muscle, sexual organs, liver, and fatty tissue of abdominal cavity were examined. Both groups showed almost same contents of lipids and cholesterol in tissue in spite of the big differences of their size and weight (Table 2). Extracted lipids, except belly fat, were separated by Bloor's method into two fractions, phospholipids (PL) and other lipids (TG), and fatty acid composition of each fraction was analyzed on GLC (Figs. 1 and 2). The data described comparatively on Table 3 could be summerized as follows: 1) In dorsal muscle TG of the wild fish, a sum of C14 and C16 acids reached more than 50% of the composition, while the cultivated fish had the acids around 40%. 2) Belly fat showed much of difference from other parts being abundant in C16:1 acid but lacking in higher unsaturated acids. The wild group contained relatively higher amounts of C14:0, C16:1, and C18:4 acids in this fat, while the fed group showed more C16:0, C18:1, C18:2 acids. Comparison of other part TG between wild and cultivated groups gave similar results as shown in Fig. 3. 3) Sexual organs of the fed group seemed to stroe C22:6 acid which was probably traced to the diet given (Table 4). However, any particular effect of other fatty acids of the feed could not be observed in the fish lipids. 4) On the other hand PL fractions which, in general, were composed of less C14:0, C16:1, C18:1, and C18:3 acids, and more C22:6 acid than TG did not show much differences among their compositions, except milt of wild fish contained less amounts of C22:6 acid than other parts.