Right now, off the coast of central Norway, some 1.5 million salmon are crammed into a single net pen the size of a football field. It’s a pilot project for an even larger design that could raise four million salmon farther out in the deep ocean.

Around the world, aquaculture has become the fastest-growing food industry. And in the decades to come, fish farmers expect to double their output. (WRI, 2014).

But that farmed fish comes at a high price to wild species. The fish you buy at the supermarket might be farm-raised, but the food it ate probably wasn’t. Some 75 percent of farmed fish is actually fed a diet containing smaller marine species, like anchovies, which come from the wild (FAO, 2018).

Yet the supply of these wild feeder fish is running out, and it’s proven too costly to raise them in captivity. One recent industry report deemed the practice of using wild fish to feed captive ones “highly unsustainable” because of the devastating effect on ecosystems. It takes five kilograms of feeder fish to create just one kilogram of fish meal. And all that seafood could feed humans instead. (Check out the interactive website behind the report at www.fishingthefeed.com.)

This conundrum has sent the aquaculture industry scrambling for new, cheaper, and more abundant sources of food. So far, their primary alternative has been adding cheap vegetable oils and plant proteins to fish pellets, which help the fish grow large but lack many of the healthy fats and nutrients found in the tissues of wild-caught species.

Now, one group of researchers is investigating a new, more drastic approach. They’ve enlisted genetic engineering to create a fish food that delivers essential nutrients that only marine species can create in nature.

But, for the reasons we’ll explore, it’s likely to fall far short of wild fish when it comes to both nutrition benefits and environmental protection.

Omega-3 Benefits

Seafood, especially wild-caught salmon, is rich in a wide variety of nutrients and minerals, from vitamin D to selenium. It’s also a vital source of omega-3 fatty acids, which our brains and bodies need for a staggering number of functions.

Yet the fish themselves aren’t the source of these nutrients — they come from the sea.

Humans can’t make omega-3s on their own, and neither can fish. So where do omega-3s come from? Like humans, fish are what they eat. Wild salmon and other species get their nutrients from gobbling up smaller fish and marine animals. At the very bottom of this food chain are plankton and microalgae, which create omega-3s.

Studies have shown that this natural diet is the reason why wild-caught seafood is such a uniquely rich source of two particularly important omega-3s: EPA and DHA. Most of the omega-3 health benefits we’re familiar with come from this pair of essential fats.

But in farmed fish, those natural sources of omega-3s can be lacking. Many farmers supplement their feed with vegetable oils, which doesn’t deliver the EPA and DHA that fish do. These alternative diets mean that omega-3 levels in farmed fish have been declining for years, according to a report by the BBC.

As the industry turns to less-healthy vegetable oils for their additives, it leaves the animals with fewer health benefits to pass on to consumers. For example, in the 1980s, farmed salmon was fed mostly fishmeal. Now, it typically makes up just 25 percent of their overall diet. That dietary shortfall has created a significant nutritional difference between farmed salmon and wild-caught salmon.

Replacing those lost nutrients is crucial for the industry’s future (Costello et al., 2020).

Some in the aquaculture industry have put their hopes in mass-producing marine microalgae or even krill that can be fed to farmed fish. But so far, those approaches have proven too expensive to be viable.

GMO Salmon Food

However, the authors of a new study published in the journal Aquaculture have spent years trying to put marine microalgae to work in a different way. The team of scientists from Norway, the United Kingdom, and Germany have genetically engineered a plant from the mustard family to produce the omega-3 fatty acids commonly found in seafood (Betancor et al., 2020).

They spliced seven genes from various marine microalgae into Camelina sativa, a flowering plant in the mustard family that’s known as a good source of ALA, a different omega-3 fatty acid not found in seafood. The scientists got it to produce both DHA and EPA, and for half a decade, they’ve been conducting trials on a handful of fish species at a laboratory in Denmark to see how the animals react to the GMO food.

So far, the team has run experiments with Atlantic salmon, gilt-head sea bream, Mediterranean yellowtail, and European sea bass. In their latest trial with European sea bass, the fish fed with GMO oils initially appeared to grow more slowly than those fed fish oil because the animals were slow to eat the food. However, both groups of fish had similar weights a few months later. And when the scientists analyzed the animals’ flesh, they found that the GMO feed resulted in increased DHA and EPA levels compared with the bass that had been fed with fish oil. But no comparison was done with wild fish; this was between two farmed fish.

No humans have eaten the fish to date. Yet, ultimately, the authors believe that their engineered plant oil could replace wild-derived fish oils without having negative effects on farmed fish growth, all while boosting omega-3 levels above those of other farmed fish.

It’s important to note, however, there is more to fish flesh than its fatty acid profile. The fish feed containing the GMO oils also has many other foods that are quite different from those consumed by wild fish. The feed containing the GMO oils also had grain products such as rapeseed and sunflower meal, and wheat and maize gluten.

Meanwhile, in the wild, salmon have access to a huge array of foods throughout their lifetimes, from aquatic insects and plankton when the fish are young, to shrimp, squid, eel, and other fish as adults, resulting in the bioaccumulation of a tremendous bounty of nutrients. Wild Pacific salmon in particular must migrate up to 7,000 miles across the ocean, as well navigate difficult journeys upriver to reach their spawning grounds.

Also, captive farmed fish typically spend their adult lives relatively immobile in one tiny patch of ocean. So, the researchers’ analysis of fatty composition in various tissues of farmed fish says little about the many ways in which the flesh of fish fed such an unnatural diet and living such an unnatural life may differ from the flesh of wild fish.

One more hurdle: for the solution to become widespread, consumers would have to be comfortable eating fish raised on genetically-modified food. And that could potentially be a tough sell. Many major grocers said they wouldn’t carry GMO salmon after one fish farming corporation won the right to raise genetically engineered salmon in Indiana following decades of legal battles. Nonetheless, that GMO salmon is due to hit supermarket shelves in the near future. It could serve as a key test for the public’s acceptance of the use of GMOs in seafood.

The Many Problems of Salmon Farming

Even as major aquaculture corporations work to create high-tech solutions, they’re also facing growing environmental challenges.

Aquaculture depends on packing as many animals as possible into fishnets and fish ponds. But those fish often don’t stay put. Unlike a cattle rancher who can chase down every lost calf, fish farmers can’t retrieve groups of salmon that escape through holes in their nets. That’s made sea lice and disease a major problem for wild salmon as their sick, captive cousins escape.

The problem is so severe that one 2007 study actually predicted a 99 percent decline in wild salmon populations if sea lice infestations continued on the same track (Krkošek et. al, 2007). Fish farms can also pollute waterways and help fuel antibiotic-resistant bacteria.

Those fears have pushed some governments to enact stricter regulations on salmon farming. In Canada, the government has ordered net-pen farming to be phased out by 2025 over concerns about water pollution and sea lice infestations that kill wild fish populations.

Additionally, advocates are pushing for aquaculture to confine its operations to places that are completely sealed off from the ocean, which are far more expensive and harder to operate. Even some modern fish farms operating on land have struggled to keep their salmon healthy. One company saw more than half a million of its salmon die at two separate sites this year. One mass death was spurred by high nitrogen levels and the other by constant construction noise.

So even if fish farming could pioneer new feeder foods that don’t depend on wild resources while maintaining acceptable nutrition quality, they’ll have to also develop new technologies to stop the spread of disease and build costly cages that keep fish from escaping.

It’s far from clear that even one of these, much less all three, can be done successfully.

In the meantime, the only reliably sustainable source of nutrient-rich wild salmon will be the tightly regulated wild fisheries of places like Alaska, where Vital Choice sources much of its seafood.

Sources:

M.B. Betancor, A. MacEwan, M. Sprague, X. Gong, D. Montero, L. Han, J.A. Napier, F. Norambuena, M. Izquierdo, D.R. Tocher, Oil from transgenic Camelina sativa as a source of EPA and DHA in feed for European sea bass (Dicentrarchus labrax L.), Aquaculture, Volume 530, 2021, 735759, ISSN 0044-8486, https://doi.org/10.1016/j.aquaculture.2020.735759.

World Resources Institute. Improving Productivity and Environmental Performance of Aquaculture: Creating a Sustainable Food Future, Installment Five. Richard Waite, Malcolm Beveridge, Randall Brummett, Nuttapon Chaiyawannakarn, Sadasivam Kaushik, Rattanawan Mungkung, Supawat Nawapakpilai and Michael Phillips. 2014

Krkosek M, Ford JS, Morton A, Lele S, Myers RA, Lewis MA. Declining wild salmon populations in relation to parasites from farm salmon. Science. 2007;318(5857):1772-5.

Food and Agriculture Organization of the United Nations. The State of World Fisheries and Aquaculture (FAO, 2018).

Costello, C., Cao, L., Gelcich, S. et al. The future of food from the sea. Nature (2020). https://doi.org/10.1038/s41586-020-2616-y