The nutrient Fish in Fish out ratio (nFIFO) specifically tracks the transfer of critical nutrients, especially omega-3 fatty acids, from feed fish to farmed fish.
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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 to improve nutrient retention in aquaculture, addressing longstanding sustainability concerns about marine ingredients sourced from wild-caught fish for aquaculture feed.
The research, published in the journal Aquaculture, details the development of a new sustainability metric called the nutrient Fish In: Fish Out ratio (nFIFO).
Unlike the traditional Fish In Fish Out (FIFO) ratio, which measures only the biomass of wild fish used relative to farmed fish produced, nFIFO specifically tracks the transfer of critical nutrients, especially omega-3 fatty acids, from feed fish to farmed fish.
Using salmon farming as an example, the researchers found that, on average, only 37.4% of the omega-3 fatty acids present in wild fish feed ended up in farmed salmon. This corresponds to an nFIFO ratio of 2.17, meaning more wild fish nutrients were required to produce fewer nutrients in farmed salmon.
Importantly, the team found that replacing traditional marine ingredients derived from whole wild fish with processing by-products - such as fish trimmings not suitable for human food - could significantly boost nutrient retention efficiency.
Such a shift could dramatically improve the sustainability of aquaculture by making better use of available marine resources and reducing waste, the researchers said.
“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 by-products in transforming marine resources into valuable nutrition within the aquaculture sector," said lead researcher Dr. Richard Newton, Lecturer in Resilient Food Systems at the Institute of Aquaculture, in a press release.
“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 added.
Study co-author Dr. David Willer from the University of Cambridge, noted, "We believe nFIFO can significantly shape more sustainable aquaculture practices, guiding producers towards resource-efficient and environmentally friendly approaches.”
To support the widespread adoption of this metric within the industry, the research team has developed a practical Excel-based calculation tool. The tool, which will soon be available online via Blue Food Performance’s sustainability indicators, is intended to help farmers and policymakers implement practices that maximize nutrient retention and minimize environmental impacts, the researchers said.
