HUFA (highly unsaturated fatty acids) content is one of the most important indices for determination of food value in fish larvae feeding. The HUFA has also an important role in fish larvae health, growth and survival. Because of this, enrichment methods for increasing of HUFA content in Artemia nauplii was developed. The aim of this study was to determine the impacts of dietary of fish and vegetable oil on Rainbow trout, Oncorhynchs mykiss, body composition. The experiments were carried out in six different treatments with three replicates for 2 weeks. The feeding treatments during the first 10 days included: 1) Commercial diet, 2) A. Urmiana nauplii enriched with fish oil, 3) A. urmiana nauplii enriched with Sunflower oil, 4) A. urmiana nauplii enriched with Canola oil, 5) A. urmiana nauplii enriched with Soybean oil, 6) Newly hatched un-enriched A. urmiana nauplii. The highest concentrations of fatty acids in diet were oleic, palmitotic, linoleic, eicosapentaenoic acid (EPA) and stearic acid, while in larvae tissue of trout in all treatments were oleic, linolenic, linoleic, stearic and docosahexaenoic acid (DHA), respectively. The concentrations of eicosapentaenoic acid [20:5(n-3)] in contrast with docosahexaenoic acid [22:6(n-3)] in the Commercial diet were significantly reduced (P<0.05). The highest concentrations of EPA was observed in nauplii enriched with fish oil in which statistically significant in comparison with the other treatments (P<0.05). The DHA content in newly hatched non-enriched nauplii and nauplii enriched with vegetable oil were zero. The results showed that vegetable oil (Canola, Sunflower and Soybean) in comparison with fish oil give more suitable results and thus, the present study suggests that early life stage of larvae growth can be feed wih nauplii enriched with Canola oil.