Omega-3 supply shifts: The case for marine agriculture

By Professor Michael Crawford

- Last updated on GMT

'Aquaculture requires feeding pellets to fish in cages, whereas marine agriculture uses sunlight as the energy source and the elemental wealth of the sea water, with no artificial input.' ©iStock/typhoonski
'Aquaculture requires feeding pellets to fish in cages, whereas marine agriculture uses sunlight as the energy source and the elemental wealth of the sea water, with no artificial input.' ©iStock/typhoonski

Related tags Docosahexaenoic acid

Varying forces are rapidly shifting the omega-3 supply chain. In this guest article, veteran researcher professor Michael Crawford says a rapid upscale in sea farming can make a major contribution to sustainable fish oils, with a potentially raised nutrient profile.

The article Global omega-3 supply set for GM plant shock​ (Nutraingredients, 20 December 2016) reported on the worrying fact that EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) has halved in farmed salmon, and that 80% of fish feed now comes from land-based genetically modified sources.

One of the chief areas of concern is trace elements. Salmon reared on land-derived feed will lose out, as trace elements are severely diminished in soils in many parts of the world. Simply adding them is not enough. They are only properly bioavailable when ingested in their natural form, tucked into proteins.

This issue of poor bioavailability has been the subject of various studies including this one​. Supplementation also brings dangers of excess, imbalance and deficiency. There is the additional concern that other trace elements suspected as being important (e.g. boron, cerium) may be omitted.

When eating fish or meat you get the trace elements in their natural form and, importantly, in the balance needed for your own enzyme systems. It is easy to get the balance wrong. There are also many competing factors and issues that affect absorption.

The fact is, fish and sea food are not just about omega-3. They are also rich in iodine, selenium, zinc, copper and manganese – all critical for brain development and function – in a form easily assimilated by humans.

Elementary issues

Iodine is essential for many aspects of biology. Without it, thyroxine cannot be made. Iodine deficiency leads to goitre and is devastating in pregnancy, leading to cretinism. Added to the mental retardation, cretinism involves facial deformities due to the lack of full brain development. There are two billion people at risk today, and these all live inland.

When I was involved in iodine deficiency studies with Dr Darwin Karyadi in Indonesia in the early 1990s there were 1m severely mentally retarded children in the country and 800,000 cases of cretinism. Some 60% of the school children had palpable goitre. None of these cases were found in the fishing villages.

In Indonesia we recommended growing kelp to provide fertiliser to put the iodine and other trace elements back into the soil. The kelp could also be used to feed livestock and people alike. Using seaweeds as food not only provides iodine and other trace elements but also a small amount of omega-3. They are now doing this in a coastal region of Bali. It is a solution to the problem; and, as it happens, the kelp farmers are actually making more money than the inland farmers.

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There are other vital players in this story, apart from iodine. Selenium is used for the seleno-proteins, which are a frontline defence for the brain against peroxidative damage. Zinc and copper are used in the Cupric-Zinc superoxide dismutase, and Manganese in Manganese superoxide dismutase. Vitamin E, of which there is very little in the brain, is protected through these enzymes. Together, the various trace elements mentioned here are critical for brain protection, and they co-exist with DHA in all sea foods.

Farming the sea

The solution is marine agriculture. This involves growing sea grass pastures on the sea bed for fish and shellfish, just as we grow grass pastures for sheep and cattle on land. Kelp forests can be grown, too. The system is sustainable, as it does not rely on feed input. Sunlight and the mineral wealth of the sea do the trick. As with land-based agriculture, you can develop sea plants to optimise productivity. Planting sea pastures also provides a safe zone for juvenile fish, so enhancing survival rates.

Making a distinction between aquaculture and marine agriculture is important here. Aquaculture requires feeding pellets to fish in cages, whereas marine agriculture uses sunlight as the energy source and the elemental wealth of the sea water, with no artificial input. 


There is a triple benefit: a sustainable source of omega-3 DHA; the by-product of fertiliser for crops; and a means of countering global warming (i.e. shellfish trap and sequester CO2, and restoration of estuarine oyster beds worldwide would be like planting rain forests).

Professor Michael Crawford
Professor Michael A Crawford is the founder and research director of the UK-based Mother and Child Foundation.

All of which I recommended to the Japanese Government in 1990. Under the direction of Dr Takahiro Tana, there is now a system slung between two islands off the coast of Okayama. With marine pastures and artificial reefs designed for the habitats and behaviour of the seven different target species, they have tripled fish production compared to what is harvested outside the zone. In addition to the fish they are harvesting oysters and mussels.

Marine agriculture is open to any nation willing and able to follow the Japanese model. 71% of the planet is water; but this resource is currently being exploited by the Neanderthal business of “hunting and gathering”.​ That idea was abandoned on land when resources began to be questionable some 10,000 years ago.

It is about time the Neanderthals’ sway in the sea was replaced too. We need to acknowledge that we live in the 21st century, with millions malnourished, and mental ill health going through the roof and getting worse. It is time to wake up from our Neanderthal slumber.

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1 comment


Posted by Dr.Christina Jeffrey,

Thank you professor Crawford for your research and service to mankind. Your efforts to awaken our world to the need for us to farm the sea beds are much appreciated. Indeed the time has come to exit Neanderthal lifestyles!

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