Alternative, ethical and locally sourced feeds can help shape the future of sustainable aquaculture

To mark the latest State of World Fisheries and Aquaculture report showing that aquaculture is now the dominant seafood-producing industry, Fish Farm Forum is getting the views of some leading figures at the forefront of sustainable aquaculture.

In the latest in the series, we catch up with Dr. Daniel Merrifield from University of Plymouth in the UK about the key role of feed in the future of the sector.

 

Just how important is nutrition as a component of sustainable aquaculture?

DM: Nutrition is central to all three pillars of sustainability in farmed animal production, whether terrestrial or aquatic. Feed, in fed-animal production, is usually the largest contributor to a farm’s ecological footprint as well as its largest operational cost. The wrong feeds or feeding strategy, therefore, compromises both environmental and financial sustainability. Furthermore, without nutritionally complete, digestible and palatable feeds, fish and crustaceans experience compromised health, leading to poor growth, increased disease susceptibility and diminished welfare.

For farming to be responsible and ethical, it is essential to prioritize the right feeds and feeding strategies that promote animal health, ensure high welfare standards and support environmental stewardship. Moreover, to achieve long-term profitability, it is crucial to implement feeding strategies that optimize feed efficiency and growth. This requires a holistic approach to nutrition — one that balances the needs of the animals, the farm’s financial health and the broader ecological impact.

 

Where are feed producers in terms of producing more sustainable feed options?

DM: The integration of more sustainable feed options in aquaculture is a critical step toward reducing the environmental impact of the industry. Different regions and producers are at various stages in this process depending on their access to resources, technological advancements and the species being farmed.

Many of the world’s leading feed producers have made significant progress in advancing sustainability. They have reduced their reliance on marine raw materials, shifted to using sustainably certified fishery products and increased the proportion of fishmeal and fish oil derived from byproducts. Producers are also embracing a growing array of alternative raw materials that, when produced responsibly, can be considered highly sustainable — such as single-cell proteins (SCPs), insect meals and algal oils.

At the feed-mill level, improving energy efficiency and transitioning to renewable energy sources are also key components of these sustainability efforts. As a result of such initiatives, we are increasingly seeing feed mills earn various sustainability certifications and accreditations, reflecting their commitment to more eco-friendly practices and greater industry responsibility.

 

What needs to change, and over what timescale do you see this happening?

DM: Aquaculture is already one of the most efficient food-production sectors across the main productivity and sustainability metrics. However, there remains scope for improvement, and large parts of the industry are working hard to this effect. To do this, further progress is required in several key areas. These changes need to happen across multiple fronts, including feed composition, resource use, efficiency, environmental impact and socio-economic considerations. The timeline for these changes will vary, but great progress can be made in the short to medium term.

We will see further efforts to reduce the use of wild-caught fish for fishmeal and fish oil with the use of fisheries byproducts and incorporating raw materials such as insect meals, SCPs, algal meals and algal oils. Increasing the cost efficiency and availability of these raw materials will be key to scaling up their use in aquafeeds, ultimately reducing the overall ecological footprint of aquaculture.

There will be greater emphasis on sourcing ethically and sustainably produced plant-based proteins that do not compete with the human food chain, while prioritizing restorative ingredients and certified products. In addition, leveraging more byproducts from agriculture and food industries will help create more circular feed systems, reducing waste and further improving sustainability.

I’d like to see a broader use of locally derived raw materials and local production of feeds which can reduce the environmental impact of transportation and support regional economies, particularly across Africa and the Caribbean. Many responsible feed producers already have targets in place to move toward these practices.

At the same time, optimizing feed efficiency is critical for minimizing waste and improving resource use. Implementing precision-feeding technologies, where fish receive diets better tailored to meet their needs, and using feed additives to enhance digestibility will maximize feed conversion. Farms have already made great progress in terms of feed delivery and monitoring systems and with the growing use of artificial intelligence we are likely to see further improvements.

I expect we’ll see significant progress over the next 5 to 10 years; indeed, many aquafeed producers and farming companies have their sustainability goals aligned to 2030, so we should see continued progress in the coming years.

 

Gut health is well-known to have an impact on the health of aquatic animals. What do we know helps in this regard, and what questions remain unanswered?

DM: Gut health is increasingly recognized as a cornerstone of overall health and performance in aquaculture. Just like in other animals, the gut plays a vital role in digestion, nutrient absorption, immune function and disease resistance. Maintaining and improving gut health in farmed fish and crustaceans is essential for enhancing productivity, reducing disease outbreaks and minimizing reliance on antibiotics or other interventions.

It is now widely accepted that functional feed additives play a crucial role in supporting or improving intestinal health. These include probiotics, prebiotics, postbiotics, paraprobiotics, synbiotics, β-glucans, organic acids, enzymes, phytobiotics and more. There is a substantial body of evidence demonstrating that such additives can positively affect the gut health of fish and shrimp.

However, not all products within each category are equally effective, and the quality of available products varies significantly. Reputable manufacturers have solid evidence bases to support the efficacy of their products; indeed, we’ve undertaken some of the research which underpins this evidence here at the University of Plymouth. Unfortunately, the market also contains products, especially in some parts of Asia, that lack credible data to support their claimed benefits. It is critical for feed manufacturers and farmers to demand robust, credible evidence before selecting products to incorporate into their feeding strategies.

Despite the advances made over the past 2 decades, many knowledge gaps still exist. We are only beginning to fully understand the complexity of the gut microbiome and how it interacts with diet, immunity and various abiotic factors, particularly for emerging aquaculture species. At Plymouth, our current research efforts are focused on evaluating the efficacy of prebiotics, β-glucans and probiotics in fortifying the microbiome, or reassembling it, after dysbiosis caused by events such as intestinal inflammation, antibiotic interventions or environmental stressors. Positive results from these studies have recently been presented at major conferences, and we expect these findings to be published in peer-reviewed journals soon.

As we continue to unravel the complexities of gut health in aquaculture, it is clear that improving our understanding of the gut-microbiome-immune-system axis is key to unlocking better health, productivity and sustainability in farmed fish and crustaceans.

 

Your long-term work on feed additives has generated a lot of publications. What have been the key findings you’d like to highlight?

DM: I can’t pick out one key aspect — all the research we have conducted has contributed positively to the wider evidence base.

Over the past 2 decades, my research group has demonstrated both localized and systemic benefits for a variety of products across more than a dozen species of fish and shrimp. Through the publication of our work, or by providing data directly to stakeholders in the case of contract research, we have helped leading functional feed-additive producers secure national and multinational authorizations for their products. Our research has also given confidence to farmers and feed manufacturers in adopting these additives.

I take great pride in knowing that our work has contributed to enhancing food security and improving the welfare of tens of millions of fish and shrimp across the industry.