Providing sustainable ways to feed the planet

Academic Spotlight: Dr Daniel Merrifield
Salmon farm in Norway
“In all of human history, we’ve never produced as much food as we do right now. But within one generation, we need another 60% more than we’re producing today. The global growth of aquaculture will be essential to that.”
Dr Daniel Merrifield has lived around the fishing industry his entire life. Growing up in Cornwall, the county’s famed ports – where he spent many an hour catching mackerel, pollock and other fish – have always been close to his heart. It enabled him to understand the varied challenges facing the industry, from declining fish stocks to falling numbers of people wanting to catch it. Through that and his studies, he came to realise the role sustainable aquaculture – alongside capture fisheries – could play in providing the planet’s 8 billion-plus people with the healthy food they need.
“We have almost 1 billion people going to bed each night hungry, and hundreds of millions of children globally suffering from nutritional and related health issues. Fish are one of the healthiest food sources on the planet; they are high in protein, low in saturated fats and usually high in omega-3s. If we can make fish more accessible to everyone, it could make a big difference.”
In addition to the formative years spent in his home county, Dan’s first flirtations with the aquaculture sector came towards the end of his degree. Always having a keen interest in science and the environment, he first came to the University of Plymouth when he enrolled on the BSc (Hons) Biological Sciences course. For his undergraduate project, he worked with Dr Colin Munn to study the chemotactic responses of Vibrio species – bacteria that cause disease in many species of fish and shellfish – to fish mucus.
Dr Daniel Merrifield
 
 
Shortly after, a PhD opportunity arose that gave Dan the chance to further that knowledge and examine some of the microbes living on – and in – rainbow trout. A project funded by BASF provided the chance to see how the science he was pursuing could have impacts on fish health and production. It is something he continues to this day, pursing a programme of applied research through partnerships with many of the leading companies working with – and within – the global aquaculture sector.
The nature of that research is, predominantly speaking, connected to fish nutrition and what feed and feed supplements different species need to thrive. It’s an emerging and expanding field, with increasing awareness of the benefits probiotics and other functional feed additives can have in aquatic species. But the diversity of fish populations, not to mention the differing nature of the waters they live in, mean there’s no quick or one-size-fits-all fix.
 
 
Whiteleg shrimp in hand
Bergen fish farm
Salmon
 
 
“Within aquaculture, there's at least 350 different finfish species, more than 80 different species of molluscs, over 60 different crustaceans and dozens of seaweeds as well,” Dan says. “It's a huge, huge industry and we haven't come close to optimising all of those production systems yet. We don't know the most optimal and efficient way of feeding and caring for all those species, and while we have made great progress for some species, for other species we’re just scratching the surface.”
As if to evidence that, Dan says he could continue his research for the next 100 years and there would still be combinations of species, rearing systems and specific nutrient requirements that would still require testing. By that time, it goes without saying, he is hopeful that sustainable aquaculture will be a successful industry in every part of the world. He acknowledges, however, that in addition to any scientific hurdles, there are also societal ones to overcome.
In regions such as Southeast Asia, aquaculture is well-established and plays a significant role in local diets. In contrast, with the exception of salmon farming, the UK aquaculture sector remains underdeveloped and contributes only a small proportion of our overall food requirements. The farming of other species, such as trout, mussels, oysters, and seaweed, has yet to reach its potential, partly due to our eating habits. As consumers, we need to broaden our palates and embrace a wider variety of species to support a more diverse aquaculture industry and strengthen our national food security. As Dan notes, salmon farming is likely the only part of UK aquaculture most people are aware of.
“I would never try to suggest that aquaculture doesn’t have environmental impacts, all forms of food production do.” Dan says. “But what is not always put across is that they are often less than many of the foods we get from land-based farming. Over the coming years, that’s one of the better balances I would like to see struck.”
 
 
 
 
One means through which Dan hopes to do that is by educating the next generation of aquaculture professionals. In addition to his research, he leads the MSc Sustainable Aquaculture and Fisheries , a programme developed in tandem with organisations and industry partners from the sector. These relationships have been forged over more than two decades and have spawned a number of research projects, student scholarships, placement years and student prizes.
The reason for such an approach is simple: it provides graduates with the best chances of being employed, and employers with the confidence those graduates possess the skills they need. Such close affiliations to the sector enable Dan to regularly shift the programme’s content to meet commercial demand. As a result of that approach, the course currently includes modules dedicated to sustainable fish production and the health and welfare of different species. But it also includes opportunities to learn about the economics of the sector, its impact on marine ecosystems, and the use of remote sensing and data monitoring.

We get a broad background of students on our MSc programme. I take great pride in the success of our graduates. They've gone on to shape current and future aquaculture practices across the globe – holding influential roles in industry, government, research and education. Their achievements are a powerful reflection of the depth and relevance of our training, and the strong, real-world connections we've built with the aquaculture sector.

Daniel MerrifieldDr Daniel Merrifield
Associate Professor of Fish Health and Nutrition

 
 
 
The use of the word 'sustainable' within the programme title is clearly planned and very deliberate. But for Dan, the only way for the entire sector to succeed is for it to have sustainability at its heart. That means ensuring that aquaculture activities – whatever they are designed to produce – have the least possible environmental impact.
“We live on a planet where 70% of the surface is water, and that’s the space we should be looking to for future food production,” Dan says. “One of the advantages of the aquatic environment is that we can farm it in three dimensions, giving us enormous potential for growth. But I don’t want someone, 50 years from now, to say we’ve done to the oceans what we’ve already done to the land – where around 40% is now used for agriculture, much of it heavily degraded and stripped of biodiversity. Striking the right balance will be a challenge, but I believe it’s both achievable and essential.”
Facilities in the fish health and nutrition research laboratories

Fish Health and Nutrition research group

The University of Plymouth has a strong research track record in the fields of fish health and nutrition dating back more than three decades.
Led by Dr Daniel Merrifield , the Fish Health and Nutrition research team works with hatcheries, aquaculture farms and various other organisations, nationally and internationally, to support and conduct research and development at fundamental and applied levels contributing to United Nations Sustainable Development Goals, 2 (Zero Hunger), 12 (Sustainable Consumption and Production) and 14 (Life Below Water).

Sustainable Aquaculture and Fisheries

At Plymouth, a broad perspective on aquaculture and fisheries management is enabled by our transdisciplinary, systems-thinking approach embraces.
From the health and nutrition of farmed fish, crustaceans and bivalves, to marine conservation, fish tracking, habitats and natural capital, our research explores how all of these diverse elements help contribute towards responsible marine and freshwater food production, and, in doing so, how they support coastal economies and contribute to the national food security agenda.
Responsible and Restorative Aquaculture