Researchers at the University of Stirling’s Institute of Aquaculture, in collaboration with the universities of Lancaster, Aberdeen and Cambridge, have developed a new method of analyzing the retention of omega-3 and other nutrients from marine ingredients, like fishmeal and fish oil, which are used as feed for farmed fish.
Aquaculture is a rapidly expanding industry, but its reliance on wild-caught fish for aquafeed has raised concerns about sustainability. Marine ingredients are vital to the transfer of nutrients and especially omega-3 fatty acids to both farmed fish and humans consuming the farmed products but are often criticized for their reliance on finite resources and feeding fish to fish practices. The new method will aid the aquaculture industry to become more efficient in retaining the valuable nutrition embodied in these limited ingredients.
Existing and widely used Fish-In Fish-Out (FIFO) metrics measure the biomass of wild fish used to produce farmed fish but fail to account for nutrient retention. The nutrient Fish-In Fish-Out (nFIFO) builds on the previous FIFO metric but includes the important aspect of nutrient retention. It also takes byproducts into account – which are not edible to humans but can be a sustainable resource for producing marine ingredients to be used in aquaculture.
The study analyzed the nutrient flow from marine ingredients through the farmed fish production system. It found that farmed salmon are currently only around 38% efficient at converting omega-3 inputs into nutrients present in commercially harvested fish.
The team identified that if all marine ingredients in aquafeeds were derived from fishery byproducts, nutrient retention efficiency could improve dramatically.
The team has also developed a calculation tool to encourage widespread adoption of the nFIFO metric within the industry. This will be made available online through Blue Food Performance’s suite of sustainability indicators.
Richard Newton, lecturer in Resilient Food Systems at the Institute of Aquaculture, who led the study, said that “unlike traditional approaches, this new nFIFO metric accounts for the retention of key nutrients in the final farmed fish, providing a more targeted means of measuring and improving aquaculture’s resource efficiency. This shift highlights the ever-more important role of byproducts in transforming marine resources into valuable nutrition within the aquaculture sector.”
“Currently retention of key omega-3 fatty acids is only around 38% and we would hope to improve that going forward. Our approach highlights the importance of promoting better feed management and circular economy principles within aquaculture, enabling the industry to make better use of finite marine resources, reduce waste, drive improvements in sustainability, and enhance the nutritional output of our farmed fish,” Newton said.
“The calculation system we have developed can be used as a practical tool for aquaculture stakeholders and policymakers to ultimately drive practices leading to lower environmental impacts while delivering high-quality farmed fish, rich in essential nutrients.”
David Willer of the University of Cambridge, a senior author of the paper, added, “We believe nFIFO can help shape more sustainable aquaculture practices. This tool allows producers to maximize nutrient retention while minimizing environmental impact.”
Reference:
Richard W. Newton, Wesley Malcorps, James P.W. Robinson, Björn Kok, David C. Little, Anneli Lofstedt, Baukje de Roos, David F. Willer. Fish as Feed: Using the nutrient Fish In: Fish Out ratio (nFIFO) to enhance nutrient retention in aquaculture, Aquaculture, Volume 602, 2025, 742332, ISSN 0044-8486, https://doi.org/10.1016/j.aquaculture.2025.742332
