The ragworm, Hediste diversicolor, is one of the few polychaeta species to present a commercial interest in Iran. In this study, the effects of six oil sources in the diet, namely fish oil (FO), soyabean oil (SBO), canola oil (CAO), corn oil (COO), sunflower oil (SFO) and mixed vegetable oil (MO), on growth, survival, fatty acid profile and biometric measurements of H. diversicolor were conducted during eight weeks. Furthermore, the mean survival rate of H. diversicolor reared on MO (82.93 ± 2.01%) diet, vice versa SGR, WG, Final biomass and PER, was significantly (p < 0.05) lower than that H. diversicolor fed the FO (89.40 ± 3.00%) diet. These findings suggested that MO could supply sufficient essential fatty acids, especially n3 and n6 and effective on zootechnical performance, survival and gonad maturation for juvenile H. diversicolor and should be given to individuals considered for production of dry feeds (and cheaper) of H. diversicolor. The results revealed a higher proportion of n3 HUFA in whole body of H. diversicolor than those in the experimental diets and values of n‐3/n‐6 in H. diversicolor fed the vegetable diets ranged from 0.13 in the COO diet to 0.21 in the CAO diet, meanwhile the values of n‐3/n‐6 in H. diversicolor fed the vegetable diets were lower than that obtained for the MO treatment. The FA such as C16:0, C17:0, C18:0 and C20:4ω‐6 had a higher concentration in experiment groups than in control. Vegetable oils, especially mix vegetable oils, were economic alternatives to the expensive fish oil used in the H. diversicolor aquaculture industry.

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