The Omega-3 Advantage of Rainbow Trout Over Salmon

Rainbow trout fillets contain higher levels of omega-3 fatty acids compared to their salmon counterparts. Recent research indicates that increasing omega-3 in the diets of rainbow trout does not enhance their health or survival in farmed conditions, yet these fish are proven to store more omega-3 from their feed when compared to salmon.

Rainbow trout and salmon share several similarities, leading to frequent comparisons between these two popular farmed species in Norway. In 2024, farmed rainbow trout represented only 6% of the total salmonid sales, while salmon dominated the market with a staggering 94%, as reported by the Norwegian Directorate of Fisheries.

“Much of the existing knowledge on salmonids primarily comes from studies on salmon. This highlights the need for specialized research focusing solely on rainbow trout,” explains Marta Bou, a scientist at Nofima.

The Importance of Omega-3 Fatty Acids

Essential omega-3 fatty acids like EPA and DHA are vital nutrients for salmonids. However, they are limited resources that must be used wisely. Earlier studies on salmon suggest that higher concentrations of omega-3 can enhance fish health and quality. Despite this, little data exists regarding the implications of high omega-3 levels for rainbow trout in commercial sea-cage farming. To bridge this knowledge gap, Nofima has collaborated with Cargill in research licensed to Hofseth Aqua. Scientific investigations have been conducted to explore how omega-3 fatty acids impact cellular mechanisms in these fish.

Feeding Trials in Sea-Cages

The research included a comprehensive sea-cage trial, where researchers tested the impact of both standard and elevated omega-3 feed levels. Fish were stocked in cages at three varied locations along Norway’s west coast, with assessments made at different times of the year to evaluate growth, welfare, survival, and fillet quality. Concurrently, a comparative study was implemented at Nofima’s research facility in Sunndalsøra, analyzing the differences in omega-3 uptake and metabolism between rainbow trout and Atlantic salmon.

“Our findings revealed distinct differences between salmon and rainbow trout. The latter effectively stores more omega-3 in its fillet than salmon consuming the same feed,” says Bou. “However, increasing omega-3 intake did not translate into improved health or production advantages for rainbow trout in these controlled conditions, unlike what we see in salmon.”

Nutritional Insights for Consumers

The research findings indicated that rainbow trout on standard feed had approximately 20 mg of EPA+DHA per gram of fillet, while those receiving the higher omega-3 feed reached around 26 mg per gram. In comparison, salmon with elevated feed levels only contained just over 16 mg per gram. According to the European Food Safety Authority (EFSA), an average adult requires 250 mg of EPA+DHA daily.

“Eating 125 grams of rainbow trout fillet fulfills my entire daily omega-3 requirement when the fish is fed standard feed. Although more omega-3 intake is possible with enhanced feeds, its overall resource efficiency remains questionable,” notes Bou.

Cargill emphasizes the critical need for ongoing rainbow trout research: “Although there are numerous similarities between salmon and trout, substantial knowledge has been exchanged over the years. This research project underscores the necessity to invest in understanding rainbow trout more deeply,” asserts Terje Utne, responsible for field trials at Cargill.