Food industry by-products could replace fishmeal in seabass diets, study suggests

Proteins made from food industry by-products could be used to reduce fishmeal use in European seabass feed, according to a study by Portuguese researchers published in the journal Aquaculture Nutrition.

The research, led by scientists from Portugal's CIIMAR, the Interdisciplinary Centre of Marine and Environmental Research, examined whether protein hydrolysates produced from by-products such as non-edible fish parts, shark skin and pork processing residues could replace part of the fishmeal typically used in aquaculture diets.

For the study, by-products were processed into hydrolysed proteins, a form in which proteins are broken down into smaller components that are easier for fish to digest. Juvenile European seabass were fed diets containing these ingredients over an 89-day trial, with part of the fishmeal replaced.

According to the study, the fish showed normal growth, maintained high feed efficiency and produced fillets with omega-3 levels consistent with nutritional guidelines for human consumption. The researchers reported that these results indicate fishmeal use can be reduced without negatively affecting growth or fillet quality, at least under experimental conditions.

One of the main findings was a marked increase in iron bioavailability. Fish fed the experimental diets absorbed up to three times more iron than those given conventional feed, the study found. The researchers said the effect is likely linked to interactions between iron and the hydrolysed proteins, which may improve mineral absorption in the intestine.

"This advancement has significant implications, promoting a more sustainable aquaculture sector that reuses by‑products, reduces waste, decreases pressure on marine resources and strengthens national self‑sufficiency in fish feed production," CIIMAR stated in a press release announcing the findings.

The work was carried out under the Pep4Fish project, which is funded through Portugal’s Recovery and Resilience Plan as part of the Blue Bioeconomy Pact, a Portuguese national public–private investment programme focused on developing the sustainable use of marine and aquatic biological resources.

The project consortium is led by the ETSA Group and includes nine partners from industry and research, including AgroGrIN Tech, B2E – Blue Bioeconomy CoLAB, CIIMAR, Seaculture, Savinor, Sorgal, Sebol, ITS – Indústria Transformadora de Subprodutos and the Escola Superior de Biotecnologia of the Portuguese Catholic University.