Adding value to ragworms (Hediste diversicolor) through the bioremediation of a super-intensive marine fish farm

The aim of this study was to evaluate the potential added value of Hediste diversicolor, cultured for 5 mo in sand bed tanks supplied with effluent water from a super-intensive marine fish farm, by comparing their fatty acid (FA) profile with that of wild specimens. The polychaetes showed an approximately 35-fold increase in biomass during the experimental period and their FA profile was significantly different from that of wild specimens. In cultivated specimens, the most abundant FA class was that of highly unsaturated FA (HUFA), with eicosapentaenoic acid (EPA, 20:5n-3) being the best represented. Similar percentage (SIMPER) analysis showed an average 20.2% dissimilarity between the FA profile of wild and cultivated specimens, supporting the view that the culture system employed enables the recovery of high value nutrients (e.g. EPA and docosahexaenoic acid [DHA, 22:6n-3]) from fish feeds into the tissues of H. diversicolor that would otherwise be lost from the production environment. While the nutritional value of wild ragworms is well established in marine aquaculture (namely for broodstock maturation diets), the higher level of DHA displayed by the specimens produced under the proposed culture system may grant them a premium market value.