Nothing wasted

Fish farming byproducts have the potential to increase the sustainability of aquaculture and contribute to other sectors – such as food, diet supplements, animal feed and cosmetics – according to a new study.

Researchers from the University of Stirling’s Institute of Aquaculture have found byproducts – such as fish heads, frames, trimmings, skin and organs – are an underused resource that could support the sustainable growth of Europe’s aquaculture sector.

As part of the Green Aquaculture Intensification in Europe (GAIN) project, Stirling PhD researcher Wesley Malcorps has found that a large proportion of commonly farmed species – Atlantic salmon, European sea bass, gilthead sea bream, common carp and turbot – were being routinely wasted in industrial and household processing.

Malcorps says: “Although fish byproducts don’t sound appetising, they are full of goodness and can be used for many purposes – including in food supply and diet supplements. Our results show a substantially higher total flesh yield (64–77%) can be achieved if fish are fully processed, compared with fillet only (30–56%), as is often the case.

“Heads, frames and trimmings from all species show potential to increase the food supply in soups or processed foods such as fish fingers, sauces and fishcakes. They could also be processed into food extracts and nutraceuticals – such as protein powders, fish oil and collagensupplements – potentially producing a higher economic value.”

He adds: “Organs can be used in animal feed, as can skin, due to its high protein, low ash content. With their high level of valuable omega-3 fatty acids, feeding byproducts to livestock would also contribute to nutrition in the human food chain, and byproducts can also be used in pet food too.”

Importantly, the current 33% of byproducts that is used in fish feed – such as fishmeal, fish oil and protein hydrolysate – could be increased, which could greatly reduce aquaculture’s reliance on wild-caught fish.

Malcorps says: “European aquaculture is dependent on imported feed from marine and terrestrial systems, such as fish meal, oil and soy, particularly for carnivorous species such as salmon. Substituting plant for marine ingredients just shifts the impact from sea to land, and also risks compromising the health and welfare of the cultured animal.”

Finally, the study shows potential industrial uses of byproducts in cosmetics, pharmaceuticals and packaging.

“Fish skin offers potential for extracting collagen and gelatine as an alternative source to cattle or pigs,” Malcorps adds.

Fish skin also has potential for use as fish leather for the fashion industry.

The study was overseen by Professor Dave Little, also of the Institute of Aquaculture, who says: “Using the whole fish is a key component of the sustainable intensification of seafood. There are issues to address in terms of technology and infrastructure, which would need capital investment to resolve, but our analysis indicates that byproduct separation could add value and nutritional efficiency.

“It could increase aquaculture’s output without using more resources.”

The paper, “Nutritional characterisation of European aquaculture processing by-products to facilitate strategic utilisation”, is published in the journal Frontiers in Sustainable Food Systems. It can be viewed online at bit.ly/byprod2021

Wesley Malcorps