In order to enhance growth, survival and quality during early juvenile stages of marine fish it is important to avoid lipid oxidation problems that are known to cause pathologies and disease. The aim of the present study was to characterise and compare the antioxidant systems in juvenile marine fish of commercial importance in European aquaculture, namely turbot (Scophthalmus maximus), halibut (Hippoglossus hippoglossus) and gilthead sea bream (Sparus aurata). The experiment investigated the interaction of the dietary antioxidant micronutrient, vitamin E, with antioxidant defence systems. Fish were fed diets of identical unsaturation index supplemented with graded amounts of vitamin E. The relationships between dietary and subsequent tissue vitamin E levels were determined as well as the effects of vitamin E supplementation on lipid and fatty acid compositions of both liver and whole fish, on the activities of the liver antioxidant defence enzymes, and on the levels of liver and whole body lipid peroxidation products, malondialdehyde (thiobarbituric acid reactive substances, TBARS) and isoprostanes. Growth and survival was only significantly affected in sea bream where feeding the diet with the lowest vitamin E resulted in decreased survival and growth. A gradation was observed in tissue vitamin E and PUFA/vitamin E levels in response to dietary vitamin E levels in all species. The activities of the main radical scavenging enzymes in the liver, catalase, superoxide dismutase and glutathione peroxidase generally reflected dietary and tissue vitamin E levels being highest in fish fed the lowest level of vitamin E. The indicators of lipid peroxidation gave consistent results in all three species, generally being highest in fish fed the unsupplemented diet and generally lowest in fish fed the diet with highest vitamin E. In this respect, isoprostane levels generally paralleled TBARS levels supporting their value as indicators of oxidative stress in fish. Overall the relationships observed were logical in that decreased dietary vitamin E led to decreased levels of tissue vitamin E, and generally higher activities of the liver antioxidant enzymes and higher levels of lipid peroxides

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The total lipid content in Artemiajranciscana (21-23% of dry weight (DW» when enriched with either Super Selco or DHA Selco was twice as high as in the adult copepods Temora longicomis and Eurytemora sp. (9-11 % of DW). In Brachionus plicatilis the total lipid content was 11 and 6.6% for cultures growing at high and low growth rate, 0.12 d-1 and 0.38 d-1 , respectively. In the copepodid stages I, II and III of Calanusfinmarchicus the total lipid level was 12-13%, increasing to 24% in copepodid stage IV, V and the adults. In T. longicomis and Eurytemora sp. the predominant fatty acids were DHA (22:6n-3), EPA (20:5n-3) and the saturated fatty acid 16:0, which constituted 40-45%, 21-24% and 8-12% of total fatty acids, respectively. C. finmarchicus contained the same dominant fatty acids. In both the cultivated live feed organisms DHA, EPA and 18:1 were the predominant fatty acids. In A. franciscana the content of these fatty acids varied according to the enrichment medium and in B. plicatilis according to the growth rate.

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The aim of this study was to compare the nutritional composition and effects of short periods with cultivated copepod nauplii versus rotifers in first‐feeding. Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae were given four different dietary regimes in the earliest start‐feeding period. One group was fed the copepod Acartia tonsa nauplii (Cop), a second fed enriched rotifers (RotMG), a third fed unenriched rotifers (RotChl) and a fourth copepods for the seven first days of feeding and enriched rotifers the rest of the period (Cop7). Cod larvae were fed Artemia sp. between 20 and 40 dph (days posthatching), and ballan wrasse between 36 and 40 dph, with weaning to a formulated diet thereafter. In addition to assessing growth and survival, response to handling stress was measured. This study showed that even short periods of feeding with cultivated copepod nauplii (7 days) had positive long‐term effects on the growth and viability of the fish larvae. At the end of both studies (60 days posthatching), fish larvae fed copepods showed higher survival, better growth and viability than larvae fed rotifers. This underlines the importance of early larval nutrition.