Higher EPA and DHA levels in feed improve salmon welfare and sustainability: EFFOP’s analysis

A newly published study in Frontiers in Marine Science provides further evidence that the value of EPA and DHA in aquaculture diets extends well beyond simply meeting minimum nutritional requirements.

The study by Catt et al., (2026) analysed commercial production data representing more than 430 million Atlantic salmon across 556 production generations in Norway between 2013 and 2023. Rather than relying on a conventional controlled feeding trial, the authors combined feed composition with commercial production data to examine how different dietary EPA+DHA levels were associated with survival, feed efficiency, harvest quality and, importantly, the consistency of these outcomes under real farming conditions.

Salmon populations receiving diets containing more than 9% EPA+DHA as a proportion of total fatty acids had 8% lower mortality than populations receiving less than 7%. Economic feed conversion ratio (eFCR) was also 13% lower, declining from 1.26 to 1.10.

Perhaps equally important was the effect on consistency. Variability in mortality was reduced by 50%, while variability in eFCR declined by 27%. Higher EPA+DHA was therefore associated not only with better average biological performance, but with more predictable performance between salmon populations.

From nutrient requirement to nutritional functionality

Much of the discussion surrounding aquaculture feed ingredients has historically focused on whether the nutritional requirements of the animal can be met while progressively reducing dependence on finite marine resources. That has undoubtedly driven considerable innovation in feed formulation.

However, meeting a minimum requirement is not necessarily the same thing as providing an optimum diet.

EPA and DHA are biologically active nutrients involved in membrane structure and function, metabolic processes and the regulation of inflammatory responses. The authors note that dietary levels historically considered sufficient to prevent deficiency – around 3–5% of total fatty acids – may therefore not necessarily provide optimum physiological robustness when salmon are exposed to the environmental, health and handling challenges encountered during commercial production.

The scale of the present dataset makes this particularly interesting. Controlled nutritional trials remain essential for establishing biological mechanisms, but commercial farming introduces combinations of temperature, disease, parasite pressure, handling and other environmental stresses that are difficult to reproduce experimentally. Here, the benefit associated with higher EPA+DHA appears not simply as increased production, but as greater biological resilience and predictability across heterogeneous commercial conditions.

Quality matters as well as quantity

The effects were also visible in the harvested product. Higher EPA+DHA diets were associated with a 2% increase in salmon achieving the “Superior Harvest” grade. In the separate processor dataset, salmon receiving higher EPA+DHA levels showed 7% fewer melanin spots and 40% fewer blood spots.

These observations further demonstrate why nutritional value cannot adequately be described by tonnes of ingredient alone. The functionality of the nutrients supplied – and their consequences for animal performance and final product quality – also matter.

What does this mean for marine ingredients?

Fish oil has historically been the principal source of EPA and DHA used in aquaculture feeds. Global supply, however, is naturally constrained and subject to biological variability. The development of additional sources of long-chain omega-3 therefore has an important role in allowing aquaculture production to grow without simply redistributing a limited pool of EPA and DHA.

The results of this study should consequently not be interpreted as an argument for one omega-3 source over another. Rather, they strengthen the case for recognising EPA and DHA themselves as strategically valuable nutrients.

Fish oil is not simply a source of dietary energy. It is one of the world’s major naturally occurring sources of preformed EPA and DHA, in many cases, produced from responsibly managed fisheries and an increasing proportion of fish-processing by-products. The productive value associated with these nutrients should therefore form part of how we understand the resource efficiency of marine ingredients.

At the same time, novel omega-3 sources can complement marine oils by increasing the total pool of EPA and DHA available to aquaculture. This complementary role may be particularly important during periods of reduced marine oil availability, such as during El Niño years, when disruption to major fisheries can temporarily constrain global fish oil supply. With global aquaculture continuing to expand, maintaining and making efficient use of existing marine omega-3 resources, while developing additional sources of EPA and DHA, should therefore be viewed as complementary rather than competing objectives

EFFOP analysis

The study is observational, and this is important when interpreting the magnitude of the reported effects. Dietary treatments were not randomly assigned, and the authors acknowledge that other nutritional variables – including dietary lipid and energy levels, micronutrients and other fatty acids – could not be incorporated consistently across the dataset. The study therefore demonstrates associations rather than definitive causation.

Nevertheless, the scale of the dataset makes the findings difficult to dismiss.

More than 430 million salmon provide a powerful commercial complement to the experimental literature showing the importance of EPA and DHA in promoting growth, health, robustness and product quality.

Perhaps the most important conclusion is therefore broader than the question of how much fish oil should be included in a salmon diet.

As aquaculture feeds become increasingly diverse, sustainability needs to be considered across the full production system. The environmental footprint of feed ingredients remains a fundamental part of this assessment, and one where responsibly sourced marine ingredients perform strongly. However, the present study demonstrates that the sustainability contribution of an ingredient does not necessarily end at the feed mill. Its nutritional functionality can also influence feed conversion, survival and ultimately the quantity of resources required to produce each kilogram of harvested fish. This is particularly relevant for marine ingredients as concentrated sources of highly functional nutrients. Where these nutrients improve biological performance and resource-use efficiency, their contribution to sustainability extends beyond their own- already low- environmental footprints to the efficiency of the production system in which they are used.

The results presented by Carr et al. provide further evidence that, for EPA and DHA, that value can extend well beyond their inclusion rate in the feed.

Carr, I., Arnott, S., Le Gal, Y., Chen, A., Costantino, J. & Santigosa, E. (2026). Higher dietary EPA & DHA levels improve commercial salmon farming productivity, predictability and sustainability. Frontiers in Marine Science, 13, 1924168. DOI: 10.3389/fmars.2026.1924168.