With collaboration from colleagues in the Universities of Stirling, Lancaster, Aberdeen and Cambridge, Dr Richard Newton has published a new article in the journal Aquaculture, proposing a new metric to measure the efficient utilisation of marine ingredients in aquaculture feeds.

The new approach is based on the well-established measures of “fish-in-fish-out” but additionally calculates the proportion of omega 3 fatty acids (EPA and DHA) fed, that are retained in the cultured fish (nFIFO). Calculations presented in the paper indicate this is usually around 37%, but that this includes if a higher proportion of the marine ingredients comes from processing byproducts rather than whole fish.

Example of mapping nutrient flows and retention from ingredients through feeds to 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.

In the interim, as a supplement to the academic paper, a simple to use spreadsheet has also been made available so that feed formulators, policymakers or other researchers can calculate nFIFO based on the proportions of different input ingreedients, feed conversion ratios and average ingredient prices.

A more comprehensive article about the research can be found on the University of Stirling website, and the journal article and spreadsheet at DOI 10.1016/j.aquaculture.2025.742332

Banner photo by kate estes on Unsplash