New metric from Stirling aims to help fish farmers boost nutrition retention

Stirling researchers seek to help fish farmers measure feed efficiency

Scientists in Scotland have developed a new method for measuring how efficiently farmed fish retain key nutrients from their feed – a step that could lead to more sustainable aquaculture.

Researchers at the University of Stirling’s Institute of Aquaculture, in collaboration with the universities of Lancaster, Aberdeen and Cambridge, have created a tool to track the retention of omega-3 fatty acids and other essential nutrients from marine ingredients like fishmeal and fish oil. The research could help fish farmers improve feed efficiency, reduce waste and lessen the industry’s dependence on wild fish, offering a path toward more sustainable seafood production.

The researchers’ approach builds on the widely used Fish-In Fish-Out (FIFO) metric, which measures the amount of wild fish needed to produce farmed fish. However, traditional FIFO calculations overlook an important factor: how well farmed fish retain the nutrients from their feed.

The new nutrient Fish-In Fish-Out (nFIFO) metric addresses this gap by incorporating nutrient retention into the equation. It also considers the use of by-products – materials not suitable for human consumption but valuable for creating marine ingredients – offering a more complete and realistic picture of aquaculture’s environmental footprint.

“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,” said Dr. Richard Newton, study lead and lecturer at the Institute of Aquaculture. “This shift highlights the ever more important role of by-products in transforming marine resources into valuable nutrition within the aquaculture sector.”

The study, published in Aquaculture, examined how nutrients from marine ingredients move through the farmed fish production system. The researchers found that farmed salmon currently retain only about 38 percent of the omega-3 provided in their feed, meaning a significant portion of these valuable nutrients is lost before the fish reach market size. This inefficiency highlights the potential for improving feed formulations and farming practices to make better use of limited marine resources.

“Currently retention of key omega-3 fatty acids is only around 38 percent and we would hope to improve that going forward,” said Newton. “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 researchers found that nutrient retention could be significantly improved if all marine ingredients in aquafeeds came from fishery by-products rather than whole fish. To help the industry adopt the nutrient Fish-In Fish-Out metric more broadly, the team created an online calculation tool that will be freely available through Blue Food Performance’s suite of sustainability indicators.

“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,” said Newton.

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

Read the full study.

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