Enrichment of live foods by essential nutrients such as highly unsaturated fatty acids is an important tool for improvement of larval fish quality. In this study, nutritional effects ofArtemia urmianaenriched by fish and plant oils on growth, survival rate, body compositions and resistance against thermal, salinity and hypoxic stresses in rainbow trout,Oncorhynchus mykisswere examined. Six food treatments comprising a commercial feed, non-enrichedArtemianauplii and the nauplii enriched by either of fish, sunflower, canola and soybean oils were used in triplicates. The fish fed withArtemiaenriched by fish, sunflower and canola oils had significantly higher (p<0.05) survival rate, total length, wet and dry weights, specific growth rate and lower food conversion ratio than those fed the commercial feed. However, there were no significant differences in growth indices between the fish fed fish oil-enriched and plant oil-enrichedArtemia. Minimum eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were reported in the fish fed with the commercial feed, while maximum EPA and DHA were in the fish fed canola oil-enriched and nonenrichedArtemia, respectively. The fish fed canola oil enrichedArtemiahad significantly higher (p<0.05) resistance against environmental stresses compared to fish fed the commercial diet. Results showed that the plant oils, mainly canola and sunflower oils can be used forArtemiaenrichment as a suitable substitute for the more expensive and rare fish oil for improving growth and resistance to environmental stresses in rainbow trout larvae.

Keywords: Rainbow trout,Artemia urmiana, Enrichment, Plant oils, Growth indices, Resistance against environmental stresses