Foto: Helge Skodvin / Nofima

Can algae-based salmon feed reduce sea lice infestations?

The challenges sea lice pose to the salmon industry have been in recent headlines. Can a diet based on microalgae play a role in solving these problems?

Researchers at Nofima and UiT The Arctic University of Norway were tasked by the Norwegian Seafood Research Fund (FHF) with investigating this.

“Briefly stated, we are testing whether sea lice infestations can be reduced if the fish are fed using selected Arctic microalgae, which are produced using residual heat and exhaust gas from a smeltery. Based on growth data and observations in the nutrition, it is believed that oxylipins from omega-3 work as deterrents to sea lice and other closely related organisms. Algae are primary producers of omega-3,” explains Nofima researcher Sten Siikavuopio, and research director Ragnhild Dragøy Whitaker.

Produced in a smeltery

In order to carry out the project, plenty of biomass must first be produced from microalgae. The production takes place at Finnfjord Smelteverk, located in the municipality of Lenvik in Troms County, Norway.

Alongside regular production of metal for the steel industry, the pre-industrial scale production of microalgae takes place in a reactor that holds up to 300,000 litres.

“When you cultivate microalgae so densely, you need a lot of CO2. The smeltery gives off a lot of CO2, NOx gases and residual heat, which we utilise to cultivate the microalgae,” says professor Hans Christian Eilertsen of UiT.

Eilertsen says that the algae population remains completely uncontaminated despite gases being pumped directly from the smeltery and into the algae tank.

Control testing

Through controlled processing of algae, and analyses of fish that have eaten on one of three feed types, researchers are able to control test the effects of the microalgae. These three feed types contain algae oil, fish oil and plant oil.

“While algae and fish oils are rich in marine omega-3, the plant oil contains other fatty acids than marine oils. Hence, the feed containing plant oil produces other oxylipins that we don’t believe will provide the same protective effect,” says Nofima researcher Birthe Vang.

“The research can thus give us answers as to whether it is the marine omega-3 in itself, or something special about the algae oil, that causes the fish to receive substances that function as a sort of “shield” against the lice,” she says.

It is still too early in the project period to conclude whether one feed type or the other works best.

“The salmon like it.”

Eilertsen says that the salmon eat the feed comprised of algae biomass.

“The salmon eat it, and it seems as though they like it very much,” he explains.

The UiT professor sees significant industry potential in utilising algae oil as fish feed, alternatively as an additional ingredient.

“Considering the high omega-3 content in the algae, and the areas of land that are lost due to the production of for example soy beans, the industry should, in the long term, consider replacing soy with algae,” he says.

 Marine biotechnology  

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