Evolution of body composition of European eels during their growth phase in a fish farm, with special emphasis on the lipid component

The effects of changes in the feeding regime on growth rate, body compositi on and fatty acid content of body lipids were monitored during the producti on cycle of European eels (Anguilla anguilla) in a fish farm, from elvers t o commercial size (> 100 g). A high variation in growth rate obliged periodic grading. The fat content i n the body of the eels notably increased over the study period in a direct relationship with size. At commercial size, a certain degree of sexual dimo rphism was apparent, as were differences in dorsal coloration. At this stag e, females were clearly larger than males and had a greater amount of body fat. Changes in dietary lipid composition (moist natural food, pellet foods with low and high fat content) influenced fatty-acid composition of body and mu scle lipids. No differences between sexes were recorded in this respect. In general, indices of the nutritional quality of body lipids decreased progr essively (in terms of the ratio between saturated, on the one hand, and mon o- and polyunsaturated, on the other). However, the high fat content of the eels' edible fraction provides an equally high amount of the strongly reco mmended highly unsaturated fatty acids of the omega 3 series (HUFA omega 3) .