By Daniel Merrifield
This time of the year is always an exciting period at a university – the start of the new academic year. The campus suddenly fills again with new students finding their way around, meeting classmates and lecturers, and beginning courses that for many will determine the direction of their careers.
This time it has particular significance for me. It is exactly 25 years (to the week) since I first arrived at the University of Plymouth as an undergraduate student. Watching this year’s new intake arrive has therefore prompted me to reflect not only on how much the University has changed during that quarter century, but also on the extraordinary transformation of aquaculture and aquafeeds over the same period.
The University I arrived at in 2001 was already an exciting place to study marine and aquatic sciences, but over the past 25 years, the University has invested more than UK£500 million in its estate and facilities. New buildings have appeared, laboratories have been transformed, our capacity for fieldwork has expanded. For those of us working in marine science, fisheries and aquaculture, some of those developments have been particularly significant.
The UK£19 million Marine Building gave us the remarkable ability to bring aspects of the ocean into the laboratory. Its COAST Laboratory includes one of Europe’s leading ocean-testing facilities, with a 35 × 15.5 m Ocean Basin capable of generating complex combinations of waves and currents.
The UK£5million investment in our Marine Station on Plymouth Sound gives us a dedicated teaching and research base right at the water’s edge, with wet laboratories, continuous seawater aquaria, scientific diving facilities and direct access to our research fleet. Today we operate seven research and diving vessels alongside smaller craft, supported by sophisticated oceanographic and hydrographic instrumentation. We can also deploy a multitude of remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), uncrewed surface vessels (USVs), aerial drones and towed sensor systems.
We have put these facilities to good use – in the 2025 Times Higher Education Impact Rankings, the University of Plymouth was ranked among the top 3 percent of universities globally for its contribution towards the UN Sustainable Development Goals. Particularly relevant to aquaculture and food production, Plymouth was ranked 6th in the world for Responsible Consumption and Production, within the top 7 percent globally for Life Below Water, and within the top 8 percent globally for Zero Hunger.
The changes in aquaculture over those same 25 years have been equally remarkable. In 2001, aquaculture accounted for around 29 percent of global aquatic animal production; today, it accounts for 53 percent, with farm-gate production valued at around US$370 billion. But the story of the past 25 years is about much more than simply producing more. We have seen major shifts in the species we farm, where and how we farm them and, perhaps most importantly, how efficiently we can turn resources into aquatic food.
We only have to look at shrimp to see the scale of change – global farmed shrimp production has increased approximately five-fold. Penaeus monodon dominated global production at the turn of the century and was the mainstay of shrimp farming throughout Asia, while P. vannamei remained largely associated with the Americas. Today, P. vannamei dominates globally. That transformation reflects much more than simply a change in species. The disease challenges encountered in P. monodon farming undoubtedly contributed to the shift, but it has also been underpinned by the domestication and genetic improvement of P. vannamei, the increased availability and adoption of SPF stocks, and advances in hatchery production, nutrition, biosecurity and health management. Together, these developments have enabled not only the enormous expansion of shrimp aquaculture, but also a remarkable intensification of how shrimp are produced.
Tilapia provides a similar example, with its own five-fold increase since the beginning of the century. This expansion has been enabled by the development and widespread dissemination of genetically improved strains, particularly GIFT and GIFT-derived Nile tilapia, alongside increasingly reliable production of high-quality, predominantly male seed. Improved feeds, nutrition and feeding practices, together with better water-quality, health and production management, have allowed higher stocking densities, faster growth and shorter production cycles.
There has also been a fundamental change in how the industry thinks about responsible production. When I arrived at Plymouth, independent sustainability certification in aquaculture was barely on the horizon; the ASC did not yet exist. Today, certification and assurance have become established features within many key sectors of the industry, with ASC alone encompassing more than 2000 certified farms producing around 2.7 million tonnes of seafood annually, alongside other major programmes such as GLOBALG.A.P. and Best Aquaculture Practices.
This reflects a much broader shift in expectations around how aquaculture should operate, with environmental performance, animal health and welfare, social responsibility and traceability increasingly embedded within how responsible production is defined.
25 years ago, one of the most persistent questions surrounding aquaculture was whether its continued expansion would ultimately be constrained by its dependence on fishmeal and fish oil. If aquaculture continued to grow, where would all the new raw materials come from to (at least partially) replace marine ingredients come from?
The industry has answered that question remarkably well. It’s had to, with increased demand and finite supply, fishmeal prices have increased approximately four-fold, while fish oil prices have risen by around 20–30-fold. Our basket of raw materials has become considerably larger today. Plant protein meals and concentrates, PAPs and vegetable oils are now conventional ingredients. Single-cell proteins, insect meals, algal oils, fermentation-derived ingredients and other novel and circular raw materials continue to expand the possibilities available to feed formulators.
Perhaps the most remarkable aspect of this transformation in feed composition is that it has occurred in tandem with improved FCRs. Atlantic salmon provides an excellent illustration. When I arrived in Plymouth a typical salmon diet was still composed of roughly two-thirds marine ingredients, principally fishmeal and fish oil. Today, that proportion is closer to one-fifth. In other words, we are producing considerably more aquatic animal biomass, much more efficiently, while using far less fishmeal and fish oil for each tonne of fish produced. The marine inclusion levels across aquafeeds for many other species has reduced even further.
Perhaps one of the biggest changes is how we define progress. Growth in aquaculture is no longer measured only in millions of tonnes, but increasingly, in how efficiently those tonnes are produced in terms of feed, land, water, marine resources, carbon and other environmental impacts.
Which brings me back to the students arriving in Plymouth this month. Over the next 25 years, they will undoubtedly witness changes every bit as significant as those we have seen over the last 25; those joining our MSc Sustainable Aquaculture and Fisheries course will, hopefully, play a part in shaping them.
