Fish fed to farmed salmon should also be part of our diet, the study suggests

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The public is being encouraged to eat more wild fish, such as mackerel, anchovy and herring, which are often used in farmed salmon feed. These fatty fish contain essential nutrients such as calcium, B12 and omega-3, but some are missing from our diet when we only eat salmon fillets.

In new research, scientists have found that farmed salmon production leads to an overall loss of essential dietary nutrients. They say eating more wild forage species directly could benefit our health while reducing aquaculture’s demand on finite marine resources.

The study appears in Feeding nature.

The researchers looked at the flow of nutrients from edible wild fish species used as feed to the farmed salmon they were fed. They found a decrease in six out of nine nutrients in the salmon fillet: calcium, iodine, iron, omega-3, vitamin B12 and vitamin A, but increased levels of selenium and zinc.

However, most wild forage fish met dietary nutrient recommendations in smaller portions than farmed Atlantic salmon, including omega-3 fatty acids, which are known to reduce the risk of cardiovascular disease and stroke

“What we are seeing is that most of the wild fish species that are used as feed have similar or greater micronutrient density and range than farmed salmon fillets,” said lead author, Dr. David Willer, Department of Zoology, University of Cambridge. “While continuing to enjoy eating salmon and supporting the sustainable growth of the sector, people should consider eating a larger and wider variety of wild fish species such as sardines, mackerel and anchovies to get more nutrients essentials right on your plate.”

In the UK, 71% of adults do not have enough vitamin D in winter, and teenage girls and women are often deficient in iodine, selenium and iron. However, while 24% of adults ate salmon weekly, only 5.4% ate mackerel, 1% anchovies and only 0.4% herring.

“Making some small changes in our diet around the type of fish we eat can go a long way toward reversing some of these deficiencies and increasing the health of both our population and the planet,” Willer said.

The researchers found that directly consuming one-third of today’s food-grade wild fish would be the most efficient way to maximize nutrients from the sea.

“Marine fisheries are important to local and global food systems, but large catches are being diverted to agricultural feed. Prioritizing nutritious seafood for people can help improve both diets and ocean sustainability.” said lead author Dr. James Robinson, Lancaster University.

This approach could help tackle global nutrient deficiencies, according to the team of scientists from the University of Cambridge, Lancaster University, the University of Stirling and the University of Aberdeen.

The scientists calculated the nutrient balance in edible portions of whole wild fish, used in pelleted salmon feed in Norway, compared to farmed salmon fillets. They focused on nine essential nutrients in the human diet and concentrated in seafood: iodine, calcium, iron, vitamin B12, vitamin A, omega-3 (EPA + DHA), vitamin D, zinc and selenium.

Wild fish studied include Pacific and Peruvian anchovy, and Atlantic herring, mackerel, swordfish, and blue whiting, which are traded and consumed as seafood.

The team found that these six types of feed contained a greater, or similar, concentration of nutrients as farmed salmon fillets. Amounts of calcium were more than five times greater in wild-fed fish fillets than in salmon fillets, iodine was four times greater, and iron, omega-3, vitamin B12, and vitamin A were more than 1.5 times more.

Wild forage species and salmon had comparable amounts of vitamin D.

Zinc and selenium were found to be higher in salmon than in wild forage species; researchers say these additional amounts are due to other salmon feed ingredients and are a real sign of progress in the salmon industry.

“Farmed salmon is an excellent source of nutrition and is one of the best feed converters of any farmed animal, but for the industry to grow it needs to be better at retaining the key nutrients it’s fed. This can be done with more strategic use of feed ingredients, including fishery by-products and sustainably sourced industrial-grade fish such as sand eel,” said Dr Richard Newton of the Institute of Aquaculture from the University of Stirling, whose team also included Professor Dave Little. Dr. Wesley Malcorps and Björn Kok.

“It was interesting to see that we are effectively wasting about 80% of the calcium and iodine in food fish, especially when we consider that women and teenage girls often do not get enough of these nutrients,” added Dr Newton.

Willer said: “These figures have been under-recognized by the standard aquaculture industry model of quoting Fish In Fish Out (FIFO) ratios rather than looking at nutrients.

Researchers would like to see a nutrient retention metric adopted by the fishing and aquaculture industries. They believe that if combined with the current FIFO ratio, the industry could become more efficient and reduce the burden on fish stocks that also provide seafood. The team is building a standardized and robust vehicle to integrate nutrient retention metrics into industry practice.

“We would like to see the industry expand, but not at a cost to our oceans,” Willer said. “We would also like to see a greater variety of affordable, convenient and attractive products made from wild forage fish and fish and salmon by-products for direct human consumption.”

More information:
D. Willer et al. Consumption of wild fish can balance nutrient retention in farmed fish, Feeding nature (2024). DOI: 10.1038/s43016-024-00932-z

Provided by the University of Cambridge

Summons: Farmed salmon-fed fish should also be part of our diet, study suggests (2024, March 20) retrieved March 24, 2024, from -fish-fed-farmed-salmon- diet.html

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