Docosahexaenoic acid (DHA) is a well-known dietary n-3 polyunsaturated fatty acid (PUFA) found in marine fish and organisms whose beneficial effects for human health are widely reported. However, the supply of food containing DHA is currently becoming critical due to the overexploitation of fisheries worldwide. Consequently, searching for alternative sources of DHA is a relevant issue nowadays. Viscera from cultured fishes is considered a by-product by the fishery industry and therefore discarded after fish processing. In this work, viscera from farmed marine fish (Sparus aurata and Dicentrarchus labrax) and also oil extracted from such by-products have been studied to assess their suitability as DHA sources by obtaining their fatty acid profiles. Viscera oil was used as a source for DHA purification by a simple and easily scalable chromatographic method. As a result, a highly purified DHA fraction (>99.0% DHA on total fatty acids) was obtained.Practical applications: This DHA concentrate obtained from viscera oil could be potentially used for alimentary or pharmaceutical purposes due to its lower cholesterol content compared with other known marine sources and also because only safe and legally allowed food-grade solvents have been used throughout the whole process. This way, by obtaining a high added-value product, a revaluation is given to fish by-products which are usually discarded. Abbreviations: DHA, docosahexaenoic acid; EE, ethyl ester; EPA, eicosapentaenoic acid; FA, fatty acid; FAME, fatty acid methyl ester; FID, flame ionization detector; MUFA, monounsaturated fatty acids; PCB, polychlorinated biphenyls; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids 724Eur.

This work is aimed at obtaining farmed fish designed to contain targeted PUFAs. To this end, an experiment was conducted with farmed specimens of gilthead sea bream (Sparus aurata L.), which were fed meal containing different percentages of common green bottle fly (Lucilia sericata Meigen) larvae, cultured on appropriate substrates, and then the fatty acid profiles in fish muscles were determined. Results indicate that arachidonic acid content in fish muscle is significantly increased when replacing different proportions of fishmeal by larvae from L. sericata, which contains arachidonic acid up to 10.6% of total fatty acids. Thus, larvae seem to be a suitable vector for introducing target PUFA in fish muscle and it could also contribute to reduce the use of wild fish stocks for fishmeal production.

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SUMMARY:Juvenile meagre were sampled at intervals during their first 500 days in a cage-based fish farm. Fish muscle showed a relatively low fat content (0.65-2.0%) when compared with other species of farmed fish, corroborating the consideration of meagre as a lean fish. At the beginning of the assay, saturated and monounsaturated fatty acids were in a similar proportion (approximately 30%), while polyunsaturated were close to 39% of total FAs, the n-3:n-6 ratio being of 3.8. Throughout the experiment a notable reduction in the sum of PUFA n-3 and an increase of linoleic (18:2n-6) and oleic acid (18:1n-9) was found. These changes led to a fall of n-3:n-6 ratio to values close to or lower than 1.0. Most probably, these changes reflect variations in the feeding regime applied during farming. In any case, fish offered good indices of lipid quality for human consumption. KEYWORDS:Aquaculture; Argyrosomus regius; Fatty acids profile; Muscle; n-3:n-6 ratio RESUMEN: Evolución del contenido en lípidos y ácidos grasos del músculo de la corvina (Argyrosomus regius) durante los primeros dieciséis meses de cultivo en jaulas flotantes. Se han muestreado corvinas juveniles durante los 500 primeros días de cultivo en jaulas flotantes. El contenido en grasa muscular fue relativamente bajo (0,65-2 %) en relación con otras especies de peces cultivados, lo que corrobora su consideración de pez magro. Al principio del ensayo, los ácidos grasos saturados y monoinsaturados mostraron una proporción del 30%, mientras que los poliinsaturados de un 39% del total de FAs, siendo la relación n-3/n-6 de 3,8. A lo largo del periodo experimental hubo una reducción notable de PUFAs n-3 y un incremento de ácido linoleico (18:2n-6) y, en menor proporción, de ácido oleico (18:1n-9), lo que llevó a una disminución de la relación n-3/n-6 hasta valores cercanos o menores de 1,0. Estos cambios reflejan variaciones en la composición del alimento durante el cultivo. En cualquier caso, la corvina ofrece buenos índices de calidad lipídica para la salud del consumidor.

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