Nutritional Responses of Round Goby (Neogobius melanostomus) caught from Rhine River (Germany) as a Wild Species to Different Fish Oils

This study was aimed to determine the effects of food supplementation with different levels of two types of fish oil (anchovy and menhaden oils), on growth and the composition of fatty acids and essential amino acids in muscle of a wild and alien species. In this study round goby (Neogobius melanostomus) caught from Rhine River (0.95-1.0 g fresh mass) were fed for 47 days diets containing 5% anchovy oil (AO), 5% menhaden oil (MO) or 2.5% AO+2.5% MO. Fish were cultured in indoor 40 L aquaria (12 aquaria in total). The feeding rate was adjusted to 10% of the fish fresh mass per day and water temperature was constantly maintained at 19 degrees C. After 47 days, no differences were observed in weight gain, specific growth rate (SGR), feed conversion ratio (FCR) and condition factor (P>0.05). The lowest FCR was found in AO diet. Muscle fatty acid composition was influenced by dietary fish oils, and fish fed the AO diet have shown slightly higher contents of eicosapentaenoic and docosahexaenoic acid in their muscle. Muscle amino acid composition was not affected by the diet, an except for leucine. The results indicated that addition of fish oil is important in maintaining the content of n-3 fatty acids in fish in aquaculture.