Fish oil from by-products 'would improve omega-3 retention efficiency'

New aquaculture research could improve the efficiency of retaining nutrition from feed ingredients to the production of farmed fish, paving the way for more sustainable practices in the industry.

Researchers at University of Stirling’s Institute of Aquaculture (IoA), in collaboration with the universities of Lancaster, Aberdeen and Cambridge, have developed a new method of analysing the retention of omega-3 and other nutrients from marine ingredients, like fishmeal and fish oil, which are used as feed for farmed fish.

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 rely on finite resources. Researchers say the new method will help the aquaculture industry to become more efficient in retaining the valuable nutrition embodied in these limited ingredients.

Introducing 'nFIFO'

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 previous FIFO metric but includes nutrient retention. It also takes by-products 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 Fish as Feed: Using the nutrient Fish In: Fish Out ratio (nFIFO) to enhance nutrient retention in aquaculture, published in the journal Aquaculture, analysed the nutrient flow from marine ingredients through the farmed fish production system. It found that the mean retention of omega-3 long chain polyunsaturated fatty acids (LC-PUFAs) from feed fish to salmon was 37.4 %, giving a nFIFO of 2.17.

Applying economic allocation principles as used in Life Cycle Assessment resulted in fish oil having a higher nFIFO burden but favoured the use of processing by-products as raw materials in marine ingredients. The team identified that if all marine ingredients in aquafeeds were derived from fishery by-products, 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 the suite of sustainability indicators from Blue Food Performance, a Stirling-based company that provides independent and scientifically verified sustainability assessments through a collaboration between academia and industry.

Improving resource efficiency

Dr Richard Newton, lecturer in resilient food systems at the IoA, led the Fish as Feed study.

He 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.

“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.

“The calculation system we have developed can be used as a practical tool for aquaculture stakeholders and policy makers to ultimately drive practices leading to lower environmental impacts while delivering high-quality farmed fish, rich in essential nutrients.”

Cambridge University’s Dr David Willer, a senior author of the paper, said: “We believe nFIFO can help shape more sustainable aquaculture practices. This tool allows producers to maximise nutrient retention while minimising environmental impact.”