Public awareness campaigns are promoting the consumption of wild fish like mackerel, anchovies, and herring, which are commonly used in the diets of farmed salmon. These oily fish are packed with vital nutrients, including calcium, B12, and omega-3, but they are partially lost when we consume only the salmon fillet.
Research indicates that farming salmon results in a net loss of essential nutrients. By incorporating more of these wild ‘feed’ species directly into our diets, we could boost our health and alleviate the pressure on the finite marine resources used in aquaculture.
The study delved into how nutrients are transferred from wild fish consumed as feed to the farmed salmon. The salmon fillets were discovered to have reduced levels of six out of nine essential nutrients—calcium, iodine, iron, omega-3, vitamin B12, and vitamin A. However, there were increased amounts of selenium and zinc in the farmed salmon. Interestingly, the wild ‘feed’ fish met dietary nutrient recommendations in smaller portions than farmed Atlantic salmon, particularly for omega-3 fatty acids, crucial for reducing cardiovascular diseases and stroke risks.
Dr David Willer from the Zoology Department at the University of Cambridge highlighted the superior micronutrient density and variety found in most species of wild fish used as feed compared to farmed salmon fillets. He advocates consuming a broader array of wild fish species, such as sardines, mackerel, and anchovies, to enhance nutrient intake directly from our diets.
The study revealed concerning statistics about nutrient deficiencies in the UK population, noting that 71% of adults lack sufficient vitamin D during winter, with teenage girls and women frequently showing deficits in iodine, selenium, and iron. Despite these deficiencies, salmon consumption is relatively high compared to mackerel, anchovies, and herring. Dr Willer suggests that minor dietary adjustments could significantly address these deficiencies and improve human and planetary well-being.
The research team proposed directly consuming a third of the current wild-feed fish as food would optimise nutrient extraction from marine resources. Dr James Robinson of Lancaster University prioritised nutritious seafood for human consumption to enhance dietary health and ocean sustainability.
According to a team of scientists from institutions including the University of Cambridge, Lancaster University, the University of Stirling, and the University of Aberdeen, this approach could be a pivotal solution to global nutrient deficiencies. The findings were published in the journal Nature Food.
In their analysis, the scientists compared the nutrient content of whole wild fish used in Norwegian salmon feed pellets to that of the resultant farmed salmon fillets. They focused on nine essential nutrients concentrated in seafood—iodine, calcium, iron, vitamin B12, vitamin A, omega-3 (EPA + DHA), vitamin D, zinc, and selenium.
The study encompassed wild fish, such as Pacific and Peruvian anchoveta, Atlantic herring, mackerel, sprat, and blue whiting. It was found that these species, often marketed as seafood, provided equal or greater nutrient concentrations than salmon fillets. For instance, calcium levels were more than five times higher in wild-feed fish fillets than in salmon, with similarly significant disparities in iodine and iron content.
Dr Richard Newton of the Institute of Aquaculture at the University of Stirling pointed out the inefficiencies in nutrient retention within the salmon farming industry, suggesting improvements through strategic feed ingredient use, including fishery by-products and sustainably sourced industrial-grade fish like sand eels.
The research team advocates adopting a nutrient retention metric alongside the current Fish In Fish Out (FIFO) ratios used in the industry, which could enhance efficiency and reduce the ecological impact on fish stocks harvested for human consumption. They envision an industry expansion that does not compromise our oceans’ health and promotes a wider variety of affordable and nutritious fish-based products for direct human consumption.
More information: David F. Willer et al, Wild fish consumption can balance nutrient retention in farmed fish, Nature Food. DOI: 10.1038/s43016-024-00932-z
Journal information: Nature Food Provided by University of Cambridge
