Adriatic sturgeon (Acipenser naccarii) were maintained on a commercial diet enriched either in long chain polyunsaturated fatty acids of the ω3 series (ω3 LCPUFA) or in saturated fatty acids (SFA). The effects of dietary fatty acid composition on spontaneous locomotor activity in normoxia and hypoxia (O2 tension = 10.5 ± 0.8 kPa), and on oxygen consumption (M(O) 2) in normoxia, in hypoxia (O2 tension = 6.6 ± 0.8 kPa) and during recovery were then investigated. The effects of adding supplementary vitamin E to the fat-enriched diets were also studied.Dietary fatty acid composition had effects on spontaneous locomotor activity and M(O) 2 in normoxia. Activity levels were higher in all sturgeon fed extra dietary fats (without vitamin E), when compared with control animals, but fish fed ω3 LCPUFA had a significantly lower M(O) 2 than those fed SFA, with intermediate M(O) 2 in controls. In hypoxia, sturgeon ω3 LCPUFA did not alter activity or M(O) 2 whereas those fed SFA reduced both and controls reduced M(O) 2. During recovery, both animals fed SFA and controls had a higher M(O) 2 than sturgeon fed ω3 LCPUFA. The data indicate that fish fed ω3 LCPUFA are more tolerant of hypoxia than controls or those fed SFA, as they did not reduce either activity or M(O) 2, and consumed less O2 during recovery.Vitamin E supplements modified the effects elicited by dietary fats. All sturgeon fed vitamin E had low activity levels in normoxia and hypoxia. Sturgeon fed vitamin E with ω3 LCPUFA had a higher M(O) 2 in normoxia than those fed ω3 LCPUFA alone; reduced M(O) 2 in hypoxia, and during recovery increased M(O) 2 to a rate higher than that of animals fed ω3 LCPUFA alone. In normoxia, sturgeon fed vitamin E with SFA had a similar M(O) 2 to those fed SFA alone but did not change M(O) 2 in hypoxia or during recovery. Thus, the effects of vitamin E were dependent on fat composition of the diet. Vitamin E with ω3 LCPUFA removed the beneficial effects on M(O) 2 and responses to hypoxia obtained with ω3 LCPUFA alone, but vitamin E with SFA allowed sturgeon to maintain aerobic metabolism in hypoxia, a more effective response than that observed in fish fed SFA alone.