Eating wild fish instead of using it as food in salmon farming would leave almost four million tonnes of fish in the sea, while providing an additional six million tonnes of seafood for human consumption, study finds .

Scientists studying Scotland’s salmon farming industry say using only fish by-products – such as trimmings – for salmon feed, rather than wild-caught whole fish, would bring nutritional gains and durability.

This would leave 3.7 million tonnes of fish in the sea and increase the world’s annual seafood production by 6.1 million tonnes.

The study, led by a team of scientists from the universities of Cambridge, Lancaster and Liverpool and the environmental NGO Feedback Global, is published today in the journal PLOS Sustainability and Transformation.

As the fastest growing food sector in the world, aquaculture is often touted as a way to reduce pressure on wild fish stocks. But many aquaculture fish – like Atlantic salmon – are raised using fish oil and fishmeal made from millions of tonnes of wild fish, most of which are food grade and could be consumed directly to provide vital nutrition.

The team collected data on the nutrient content of fish, the composition of fishmeal and fish oil, and salmon production, and examined the transfer of micronutrients from feed to fish in the fish industry. farmed salmon in Scotland. They found that more than half of the minerals and essential dietary fatty acids available in wild fish are lost when these fish are fed farmed salmon.

Dr David Willer, researcher in the Department of Zoology at the University of Cambridge and first author of the paper, said: “Fish and seafood provide a vital and valuable food source rich in micronutrients for people around the world. whole, and we need to make sure we use it. resources efficiently. Eating more wild fish and using alternative feeds in salmon farms can achieve this.

The team developed various alternative production scenarios where salmon was only produced from fish by-products and then added more wild-caught fish, mussels or carp for human consumption. All scenarios produced more nutritious seafood than salmon and left 66-82% of forage fish in the sea.

Feedback’s Dr Karen Luyckx said: “If we want to feed a growing world population well and sustainably, we need to stop catching wild fish to feed farmed fish. Until the salmon industry ditches its habit of wild-caught fish oil and fishmeal, chefs and retailers should help citizens ditch unsustainable salmon by offering mussels instead ultra-nutritious and small oily fish.

Based on their findings about the Scottish salmon industry, the researchers collected global data on salmon, fishmeal and oil production to apply their alternative scenarios on a global scale. One scenario shows that farming more carp and fewer salmon, using only fish-by-product feeds, could leave 3.7 million tonnes of wild fish in the sea while producing 39% of more seafood.

The authors warn that not enough is known about the source and species composition of fishmeal, but there are positive signs that the use of plant-based foods is increasing.

Dr James Robinson of Lancaster University said: “Aquaculture, including salmon farming, plays an important role in meeting global food demand, but nutritious wild fish should be prioritized for local consumption rather than for salmon feed, especially if caught in places where food insecurity is present. .

“Support for alternative feeds can facilitate this transition, but we still need more data on the volumes and species used for fishmeal and fish oil, as this can show where salmon farming is putting additional pressure on fish. fish stocks.”

Ultimately, the authors call for a reduction in feed for marine aquaculture, as this will provide opportunities to produce more nutritious seafood while reducing pressure on marine ecosystems.

Willer added: “If we want to feed the growing world population well and sustainably, we need to stop catching wild fish to feed farmed fish. There is an urgent need for the food industry to encourage the consumption of more sustainable seafood species – such as mussels or carp – which do not need other fish for food.

This research was funded by the Cambridge Philosophical Society, via a Henslow Fellowship to David Willer.

Reference
Willer, DF, et al: “Maximizing sustainable nutrient production from coupled fisheries-aquaculture systems. PLOS Sustainability and Transformation, 2022. DOI: 10.1371/journal.pstr.0000005

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