Tiny ingredient tackles big problem: Krill meal reduces melanosis in farmed salmon

Aker QRILL research shows multiple health benefits with krill meal inclusion

Melanin spots on Atlantic salmon fillets are a growing concern for salmon producers. Also known as melanosis, they are said to appear due to the fish’s immune response to inflammation caused by stress or tissue damage. Dealing with melanin spots requires the removal of affected areas, and in some cases the complete discarding of fillets, resulting in increased labor costs and economic losses for farmers.

“Approximately 20 percent of salmon on farms in Norway and 30 percent in Chile can be affected,” Ragnhild Dragøy, senior VP of product management and sustainability at Aker QRILL Company in Norway, told the Advocate. “The spots themselves do not harm salmon, but the cost to farms is big.”

As Dragøy explained, affected fish are downgraded based on the severity of the dark spots on salmon. Smaller spots are removed during processing, which will usually result in downgrading, while larger spots often result in the whole filet being thrown away.

“Downgrading and discards create a significant amount of waste as well as financial losses. It’s also difficult for farms to detect melanin spots prior to slaughter, while the appearance of fillets is an important quality feature because it influences consumer purchasing decisions. In this sense, melanin spots are a major issue.”

However, new research by Aker QRILL Company shows that incorporating krill meal into salmon feed can significantly reduce melanin spots, improving fillet quality and helping farmers maximize their returns. Krill provides the necessary amino acids for salmon to build muscle and other tissues, and vitamins and minerals to support cell function and protect tissues from damage.

It’s also a rich source of omega-3 fatty acids, including EPA and DHA in phospholipid form. These create anti-inflammatory effects, and their phospholipid form enables the uptake of fatty acids in the digestive system and their deposition in cell membranes in the tissues. In addition, krill organic forms of provides selenium and zinc–essential minerals linked to melanosis reduction. It also contains natural antioxidants like astaxanthin, vitamin E and vitamin A, all of which are beneficial for reducing melanin spots.

Through its krill-based feed ingredient QRILL Aqua, Aker QRILL Company is focusing on feed innovation and working to maximize ingredient value while supporting salmon farms. The company began its research after the publication of a study that showed that salmon given high doses of krill meal in the later production stages had better fillet quality and fewer melanin spots. Aker QRILL Company also found that krill meal gave salmon a different fat profile to other feed ingredients, and a higher functioning immune system, reducing inflammation and oxidative stress.

“Krill meal has an array of benefits,” said Dragøy. “Other examples include helping salmon take up nutrients more efficiently, and a good lipid profile in salmon fillets. These, along with a robust immune system, are key to reducing melanin spots. Krill is also an attractive ingredient to salmon because it has components that increase fish appetite and feed intake, along with osmolytes, which help salmon maintain a salt balance in varying water conditions.”

Trials by Aker QRILL have shown that adding approximately eight to 10 percent of QRILL Aqua to the diet of Atlantic salmon before transfer to sea helps eliminate melanin spots. For optimal health benefits during the grow-out stage, an inclusion rate of 8 to 12 percent QRILL Aqua is recommended.

The biggest challenge, however, is the cost of krill meal and the risk of investing in something at the start of the production cycle, said Dragøy, with the results only becoming clear during the harvest stage. Farmers also need to know how to use krill meal across different stages of the production cycle and understand the periods when krill meal works at its best, in order to gain the most benefit.

While the use of krill meal goes a long way in reducing melanin spots, Dragøy emphasized that it’s only part of the solution. Proper fish handling to prevent bruising and minimize fish stress, creating calmer rearing environments to support better growth and preventive disease management can also help. Just as important is collaboration and knowledge sharing between farms.

Can a diet that includes Antarctic krill improve sea bream larvae survival?

“We know that krill meal works well at the tested inclusion rate,” said Dragøy. “It would be interesting to further research these rates to find that ideal threshold if a farm’s issue is only melanin spots. However, melanin spots are commonly associated with other issues, such as stress, handling, disease or inflammation. These would need to be investigated separately.”

Going forward, Aker QRILL Company is continuing to research the effect of krill in several species including shrimp and marine fish, and address other barriers that farms are facing, such as climate-induced challenges and how best to apply krill feed at different temperatures, salinity or oxygen levels.

“We hope to be even more collaborative with farmers and feed companies to ensure the best, optimal use of krill feeds,” said Dragøy. “We are also looking forward to adapting as technology and aquaculture develop and new species come in. For farmers, key drivers of cost-effectiveness are growth, health and premium product quality. Krill can significantly contribute to these success factors, creating better results and playing a role in farms’ success. The key focus for us at the moment is to help meet the challenges that farms and feed producers currently face.”