The Portuguese study applies a circular‑economy approach by transforming food‑industry by‑products – such as non-edible fish parts, shark skin and pork by‑products – into high‑value feed ingredients for fish. These ingredients are obtained through a process that “pre-digests” proteins, turning them into smaller particles that are easier for seabass to absorb.

Portuguese study tests new diet for seabream

For 89 days, juvenile seabass were fed diets in which part of the fishmeal was replaced by these innovative ingredients (hydrolysates). The results showed that the fish grew normally, maintained high feed efficiency and produced a high‑quality fillet with adequate omega‑3 levels for a healthy diet. In other words, it was possible to reduce reliance on fishmeal – a limited resource – without compromising quality for consumers.

The most innovative result of the Portuguese study was the marked increase in iron bioavailability. The tested diets enabled seabass to absorb up to three times more iron than fish fed a traditional diet. In practice, this means the fish were able to utilise this essential mineral far more effectively. According to the researchers, this effect is related to the way these transformed proteins bind to iron, facilitating its 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.

Promoted by the Blue Bioeconomy Pact and funded through the Recovery and Resilience Plan (PRR), Pep4Fish represents a strategic investment to position Portugal as a European leader in the sustainable use of marine resources and in the development of more efficient, circular and low‑impact nutrition solutions.

The project consortium brings together companies and research centres working collaboratively to develop protein hydrolysates and other functional ingredients capable of modernising aquaculture and enhancing the sector’s competitiveness. It is led by the ETSA Group and includes nine partners: 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.