Development of broodstock diets for the European Sea Bass (Dicentrarchus labrax) with special emphasis on the importance of n - 3 and n - 6 highly unsaturated fatty acid to reproductive performance

Abstract

Commercially fabricated diets allow greater control over the composition of biochemical components and reduce the risks of disease introduction, which are significant concerns when using the wet fish diets commonly used for most farmed marine broodstocks. However, satisfying the dietary lipid requirements of marine broodstock using artificial diets has proved difficult, particularly with respect to their highly unsaturated fatty acid (HUFA) composition. Two groups of mature sea bass, each divided between three replicated tanks, were fed two dry pelleted diets over a 2-year period, encompassing two spawning seasons. The first diet contained a good quality Northern Hemisphere meal and oil; the second differed only in the source of oil, which was substituted with tuna orbital oil (TOO). The use of TOO in the dry pelleted formulation allowed the manipulation of n - 3 and n - 6 HUFA in the resulting eggs, specifically arachidonic acid (20:4 n - 6; AA), eicosapentaenoic acid (20:5 n - 3; EPA) and docosahexaenoic acid (22:6 n - 3; DHA). The results showed that dietary manipulation of these HUFA could improve levels and ratios of AA, EPA and DHA which were transferred to the resulting eggs with improvements in early survival and hatching success repeated over successive spawning seasons. The dry diet containing TOO facilitated comparable reproductive performance to the wet fish diet (Boops boops) which has previously been considered the most effective broodstock diet. The improvements in reproductive performance are discussed in relation to the proportion of these HUFA with respect to each other in total egg lipid and the phospholipid classes phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidylethanolamine (PE) and to their potential impact on eicosanoid formation. Finally, this study has shown that a commercially fabricated diet can be successfully used as sensitive investigative tool for aquaculture research.