
An In focus workshop analysed gaps between science and practices and use of omega-3 stocks more efficiently
A unique group of academic and industry experts in aquaculture, fish and human nutrition gathered for an IFFO In Focus workshop on May 31 in Stirling, Scotland to analyse the knowledge gaps in the omega-3 story. They covered its role in fish and human nutrition, to what and where the potential growth is, and how we can use omega-3 stocks more efficiently. Discussions focussed on the gap between science and practice, such as the inclusion rates, which are often determined in laboratory instead of farm conditions.
Opening the event, IFFO’s Dr Brett Glencross stated that the industry needs to look beyond flesh/fillet omega-3 targets, exploring what the actual requirements are for both fish and humans and how we communicate this.
Mapping the global supply of omega-3s and the potential for more
Looking at the reality and potential omega-3 supplies, Dr Richard Newton, University of Stirling presented a systems approach to quantify the global omega-3 production and utilisation pathways, the natural loss in nature and the loss in processing along the path to human consumption. In fisheries, loss can be reduced by improving the natural pathways through fisheries management. However, the greatest potential lies within aquaculture and fish processing, which currently sees a huge loss of potential by-products.
“There are a lot of inefficiencies in the value chain for most species, although in aquaculture, gains are being made in terms of nutrition, feed delivery and genetics, for some species. Only a small fraction of EPA and DHA from net fish production is actually harvested: seafood trimmings have huge uncaptured value.”

Opportunities for by-products vary greatly globally and the industry needs to carefully determine what goes to feed or direct human consumption.Looking at the potential of by-products across different regions, Newton presented findings from a IFFO development database (2013), looking at pathways, use and waste. The database showed the potential for an additional 2.5 million tonnes of fishmeal globally from by-products and this figure is expected to have increased since the data was last gathered in 2013. If all seafood was processed, the extra potential was calculated at 9.7 million tonnes, which again shows the huge waste level within the current food system. An example of this potential is that retention of omega-3s is lower in the fish fillet, with most being left in the ‘waste’. However, the data does not account for the increasing use of by-products for direct human consumption, or in pet food . More data gathering is needed on this potential and omega-3 retention in various fractions to allow the industry to better map and utilise the various products.
Identifying these marine ingredient sources and reducing loss is essential for the growth of aquaculture, which is accelerating, both in Asia and Africa. In China, seafood consumption is growing with people eating more protein and more energy dense food and reducing consumption of cereals. The market will not always be the best driver to improve nutrition and resources need to be used in a strategic way.
There is potential for species such as tilapia and grass carp, which efficiently convert alpha-linolenic acid (ALA) to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Gains are being made in terms of nutrition, feed delivery and genetics. However, inefficiencies remain across the value chain for most species and more assessments are required to identify the potential and deliver this change.
“There is a push to apply a nutritional index to life cycle assessment as an additional impact category. A big topic presently is how to measure the impacts of food from a nutritional perspective.”
Where are we with development of novel omega-3 sources? Exploring the potential new sources of omega-3s, Associate Professor Monica Betancor, University of Stirling introduced the range of new omega-3 sources under development, starting with algal biomass, which hasma limited inclusion level due to constraints with digestibility, and algal oil, which is higher in price.
EPA and DHA contents vary across the products and data is still being gathered to map environmental impacts to compare with other ingredients. Fish trials have been carried out, showing beneficial results with impacting levels on sea lice with one of the algal oil ingredients. An example of an innovative approach in this area is a DHA only biomass oil produced from pot ale (from whisky distilleries) to create a more sustainable ingredient for the pet and aquafeed markets.
Moving to genetically modified (GM) crops, they can be an EPA and DHA mix and differing commercial crops are available with trials carried out on humans and several fish species. The main plants being used are canola and camelina, but questions remain regarding the varying balance of EPA and DHA, on-going investigations into health benefits and impacts, legal challenges and public acceptance. The UK is now differentiating from the EU on the inclusion of GM crops and a new bill may open up this market.
Betancor showed other areas of innovation including precision fermentation and cell cultivation. She concluded that we need to re-assess these ingredients based on new sustainability indicators and look at direct human consumption rather than just feed inclusion.
How do omega-3 affect fish physiology?
Moving to the role omega-3s play in fish physiology, Dr Nina Liland at IMR, Norway presented findings from long-term fish trials, showing that without EPA/DHA, farmed fish are vulnerable to stress and disease. Fish are affected by both their environment and water temperature and the amount of dietary EPA/DHA required depends on both these factors and how they adapt their membrane to the temperature. Diet is more impactful on the fatty acid composition of Atlantic salmon than the water temperature. Fish can handle lower levels but there is a baseline, as too little EPA and DHA changes the fatty acid composition in essential organs.

A study by Hundal et al. (2022) showed the close relationship between omega-3 and omega-6. Given their role in impacting cell membrane structure and gut, bone, gill, and skin health, the balanced inclusion of EPA and DHA is vital to improving resistance to inflammatory diseases. These positive effects are still being mapped on skin health, which is very important in a farming environment and EPA and DHA have been shown to promote tissue integrity.
Trials have shown that a low EPA and DHA diet impacts astaxanthin deposition and increases fat content in the liver, intestine, and viscera, leading to reduced intervertebral space and caused hyper-vacuolisation of the intestinal cells. Additionally, EPA/DHA impacts corticosteroid regulation. However, there are complex interactions in the synthesis of other steroids. The new sources of EPA and DHA have a huge variation of EPA/DHA ratios, which provides a challenge in feed formulations. The benefits of EPA and DHA are extremely complex and are still being investigated; what is clear is that ensuring a balanced inclusion of both, along with balanced inclusion of omega-6, promotes fish health.
What is the market doing with regards to the omega-3s?
Starting with global production, IFFO’s Enrico Bachis, noted that supply has remained steady since 2010 of around 5 million tonnes of fishmeal and 1 million tonnes of fish oil. Latin America, most notably Peru, still leads in fishmeal production, whereas fish oil production is led by Asia and then Europe, with the difference due to the variation of fat content to produce fish oil. The use of by-products continues to rise, with 34% of global fishmeal supply coming from by-products and 53% of global fish oil supply coming from by-products in 2023. The EPA and DHA markets differ from the fish oil markets again due to the variation of EPA and DHA in the raw materials.
In terms of the main sources of crude oil, anchovy (from Peru and Chile) continues to lead, followed by sardine and menhaden (USA). Sources of crude oil are diverset and production of algae-based EPA and DHA is increasing.
Aquaculture is a major consumer of fish oil
In terms of demand for fish oil, looking at 2021 figures, aquaculture consumed 74%, direct human consumption (supplements) consumed 16% and petfood consumed 10% in 2021. Demand for aquafeed continues to increase and marine ingredients are now considered a strategic ingredient with a critical role within a broader raw material basket. Demand is growing fastest with crude oils, with an average growth prediction of 2.5%/year to 2025. In general market demand for fish oil is diverse and prices have reached record levels, with stock availability especially impacting the pharmaceutical sector. This demand is pushing for further strategic use.
What can we learn from human omega-3 physiology
Moving the focus to humans, Professor Philip Calder, University of Southampton explored lessons learned from human omega-3 physiology. EPA and DHA provide special and unique biological properties to humans, changing the physicality of the membrane and its function, changing protein and lipid function and structure in a more optimal way. This changes gene expression patterns, altering when proteins are produced, cell responses and activation and “raft” assembly in the cell membrane, which affects the way in which proteins and cell membranes function. The overall benefit to this is the reduction of inflammation which then benefits different organs throughout the body, including aiding visual function, cognitive function, metabolism, inflammation regulation, immune responses, oxidative stress, blood coagulation, organ function (e.g. heart, liver, lung, muscle) and wound healing.

EPA and DHA are generally poorly synthesised in humans, so their inclusion in our diets is essential. EPA is typically absorbed faster than DHA, but DHA is biologically more stable, so it is retained in the body for longer periods. In terms of dose, short term impacts can be seen with high consistent doses with longer retention, but over longer periods, fluctuating doses are still beneficial.
Consumption of EPA and DHA is especially essential during pregnancy and early development, especially with breast feeding. In terms of a hierarchy of anti-inflammatory effects of fatty acids, EPA and DHA are most effective, followed by stearidonic acid (SDA) and ALA, the last being the least involved in anti-inflammatory responses in the body. Highly controlled laboratory experiments have indicated that for some processes (e.g. inflammation) DHA is more potent than EPA and that plant omega-3s have low bioactivity (low conversion to inflammation mediators), although the latter is still being explored.
What do we know about the omega-3 requirements in Atlantic salmon?
Exploring the latest science on omega-3 inclusion in salmon feed, Dr Bente Ruyter (NOFIMA) discussed the impacts on growth, health, and quality. Studies have shown that dropping EPA and DHA inclusion in salmon feed below 1% of the diet leads to reduced survival, fatty liver, intestinal pathology, and deformities of vertebrae. Bente presented the results of a trial carried out on Atlantic salmon in sea cages to assess the impacts of varying levels of EPA and DHA, and improvements to growth, welfare, robustness, and fillet quality.
Using four diet groups of differing levels of EPA and DHA in the feed (1%, 1.3%, 1.6 and 3.5%), results showed that fish in the high omega-3 group outperformed the others. Growth rates were unaffected at early stages in the trial, but the high EPA and DHA groups grew fastest by the end and had higher EPA and DHA retention rates.
In terms of overall health, benefits of a high EPA and DHA diet were seen in the muscle, liver, hindgut and skin. Other studies showed that lowering the fat content in the diet, along with increasing EPA helped with heart health in fish. Resilience to disease was also higher in fish fed high EPA and DHA diets with lower mortality observed. In terms of rates in mineral uptake, EPA and DHA improved absorption throughout the body, especially of selenium and zinc.
Fillet quality was also improved with this group, including the colour, muscle firmness and incidence of gaping. Overall, studies have shown that the requirement of EPA and DHA in Atlantic salmon diets is higher than previously thought and played an important role in health, growth and quality.
What do we know on requirements for marine fish?
Glencross also explored omega-3 requirements for marine fish. Responses vary across species, notably greatly differing from Atlantic salmon and again requirements also change across the life cycle. In general, without EPA and DHA, there is growth retardation and essential fatty acid retention also drops. Smaller fish need more omega-3s and increasing the level of ARA results in poorer growth in some species, and DHA alone produces only nominal improvement.
Data is still lacking on the influence of 18:2n-6 on LC-PUFA requirements, and the role EPA and/or DHA in immune function needs further clarification. Finally, there are few quantitative models on maximising the uptake and retention efficiency.

Conclusion
The role of EPA and DHA varies across species, but in general they remain essential in most aquaculture species and for human health. It is evident that we are not underestimating their importance in aquaculture and the continued strategic inclusion of these nutrients in aquaculture diets demonstrates this.
Emerging shortages can potentially be addressed with increasing production from by-products and ensuring their strategic use between feed and direct human consumption. Alternative ingredients appear unlikely to fill the current gap in omega-3 demands. However, algal products do show potential; due to fish oil price increases and they are beginning to make a notable contribution, but GM ingredients still appear some way off. Lessons can be learned from both the human and aquaculture sectors to fill the science gaps, especially on biological markers.
This article was contributed by the IFFO team and was first published in the print edition of Aqua Culture Asia Pacific (November/December 2023)