Richard Newton, Wesley Malcorps, Bjorn Kok and David Little recently worked with colleagues from the Universities of Cambridge, Lancaster and Aberdeen to look at how micronutrients in feed fish could be most efficiently utilised for human nutrition. The study was funded by the Scottish Government, Royal Society, Leverhulme Trust, Henslow Fellowship and the University of Cambridge and led by Dr David Willer of the University of Cambridge.

Farmed Atlantic salmon is an excellent source of nutrition, and is one of the best converters of feed of any farmed animal. While farmed Atlantic salmon is considered a net neutral consumer and producer of fish biomass, it uses more of certain key nutrients than it produces for human consumption. Therefore, it is crucial to develop a better understanding of the interlinkages between aquaculture and capture fisheries and how we can optimise nutrient availability for the global human population.

Focusing on nine micronutrients, the team found that six of these (iodine, calcium, iron, vitamin B12, vitamin A and omega-3 (EPA+DHA) are found at higher density in wild caught species that are used in aquafeeds such as sardines, mackerel and anchovies than in farmed salmon fillets. On the other hand, farmed salmon contained higher concentrations of zinc and selenium and equivalent concentrations of vitamin D.

The team recommend the development of a nutrient retention metric which could be adopted by the fishing and aquaculture industries. When combined with Fish-In-Fish-Out metrics, this could help optimise the use of capture fishery feed species and processing by-products. One aim would be to find ways of ensuring farmed species are better at retaining the key nutrients that they are fed. The direct consumption of around one third of current food-grade wild feed fish would also help to maximise nutrient gain from the sea.

Overall the study indicated the greatest benefits by encouraging consumption of the edible portion of wild fish but ensuring their processing wastes are used in aquafeeds.

Read more in this Springer Nature Blog or University of Stirling News Post and in the full study published in the journal Nature Food - Wild fish consumption can balance nutrient retention in farmed fish.