Surf and turf

With all types of food production under fire for their environmental credentials, experts from both aquaculture and agriculture have joined forces to say a solution lies in greater collaboration.

According to the multidisciplinary team of scientists, integration between fish and arable farming could provide the sustainable food production the world needs – for example, by using genetically modified (GM) crops to meet the nutritional demands and expanding growth of global aquaculture.

Their innovative approach is outlined in a new paper – published in Nature Foods – with plant scientists from Rothamsted Research teaming up with aquaculture experts at the Universities of Stirling and Trondhiem. It follows a series of collaborative studies conducted by the three institutions looking at the impact of new feed types for farmed Atlantic salmon.

Last year’s landmark EAT-Lancet report stated that humanity needs to move away from animal protein towards a much more vegetarian diet as the only way to operate within planetary boundaries. At the same time, it suggested global fish consumption could be increased sustainably - but only if wild populations are protected from over-fishing.

Whilst farm reared fish would appear to be the answer, they too need a sustainable feed source say the group, and one that doesn’t compromise the nutritional content of the fish.

Lead author Rothamsted’s Professor Johnathan Napier said: “Agriculture and plant biotechnology have the potential to radically transform aquaculture, by providing new sources of important nutrients such as omega-3 fish oils in a manner that is not constrained by limited natural resources.

“The scalability of agriculture also means that supply can much better meet demand, helping aquaculture to further expand but without compromising either the environment or the nutritional quality of the fish. 

“Today we are proposing a more synergistic relationship between agriculture and aquaculture that will ultimately help us meet the recommendations of the EAT-Lancet report and the sustainable provisioning of the proposed ‘Planetary Health’ plate."

Aquaculture feeds are historically based on fishmeal and fish oil – both extracted from wild fish, however, the global expansion of aquaculture has meant that this practice has become unsustainable worldwide.

While terrestrial animal by-products – such as poultry meals, blood meal and tallow – have been used in some parts of the world, primary alternative ingredients have been derived from plant seed meals and vegetable oils.

Co-author Dr Monica Betancor, a fish nutritionist at the University of Strirling, said: “Fish feeds are becoming more plant-based and this impacts the nutritional profile of farmed fish. Plant biotechnology could offer a greener, sustainable future for aquaculture by providing beneficial omega-3 for fish and, in turn, boost levels in the human diet.”

As the nutrient composition of farmed fish is altered, there are also consequences for human nutrition – including reductions in minerals, such as iodine and selenium; vitamins, such as vitamin D; and most significantly in the beneficial omega-3 fatty acids.

Rothamsted have pioneered using GM crops to produce some of the specialised feed ingredients that aquaculture is dependent on, namely omega-3, and the research team have conducted a number of studies in recent years, specifically considering the viability and impact of using oils from GM oilseed crops in fish feed in providing the omega-3 long chain polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Professor Napier says that ultimately, the two systems – aquaculture and agriculture – will need to work in tandem to meet the challenges of operating within planetary boundaries and delivering optimal nutrition for a growing population.

He said: “It is our hope that the ideas outlined in this paper are just the starting point for a more integrated approach to sustainable aquaculture, one in which the major role of agriculture is fully incorporated.”

You can access the full paper free here