Farming the fishes for the dishes: how sustainable is aquaculture?

by | Dec 9, 2021 | Opinion

In part 3 of a whistle-stop tour through sustainable seafood, Vincent stops to check in on the fish farmers

This winter I broke my rule. I’ve been on an eat-no-seafood stance as a tiny protest against overfishing and, you know, all that ocean stuff. Brave? Pointless?  I feel like the proverbial ‘old man shaking fist at cloud’.

But standing on the edge of the icy ponds at High Country Salmon in Twizel in July this year, it simply was not possible to walk away empty-handed. The pristine water boils with silver-skinned chinook salmon and the fridges are chocked full of omega-rich, tender pink meat. The $80 fillets fed our family of six for two days and made great snacks on the ski fields (why did it take us so long to realise that sushi is great for ski trips). Even my vegan son admitted the fish looked happy, if not delicious.

We know all too well how fast the stocks of wild seafood are declining. And we know that our appetite for kai moana and all things fishy continues to grow. Enter the age of the fish farmers. Aquaculture is experiencing the equivalent of a surface boil-up – has been since the 1980s. Already half of the world’s seafood comes from aquaculture and the UN’s Food and Agriculture Office predicts volumes will grow 32% again by 2030. Check out this graph:

That’s good, right? More fish in the farms means more in the sea and more for me.

Kind of. The environmental footprint of fish farming is massive and the industry comes with a boatload of problems. When tons of fish are crowded together, they create a lot of waste, which can pollute the ocean. Fish farms can be breeding grounds for disease and escaped fish can infect wild stocks as well as humans. Coastal farms compete with other activities for share of space. Expansion of land-based farms can destroy ecosystems in the same way that agriculture does. This is especially true of China and parts of South East where carp and shrimp farms push hard against human and animal habitats. Shrimp farming in Indonesia is at least partly responsible for the region’s declining mangrove forests.

The biggest issue is that it takes a lot of wild fish to feed farmed fish. It’s a circular economy gone wrong: catch the fish to farm the fish.  Carnivores such as salmon and catfish rely on a complex mix of ingredients called fishmeal made largely of chopped sardines and other tasty bits. Here’s a graph showing just how much fishmeal is consumed globally. The good news is that as aquaculture science improves the reliance on fishmeal is declining.

Feed is also the major source of greenhouse gas emissions in the industry, with 50-60% coming from catching and distributing fish food. Compared to other forms of protein, fish farming has a much lower emissions profile totaling about 0.5% of total global emissions, similar to sheep farming. Per kilogram of protein, though, it’s similar to beef on a global average basis.


Where’s NZ at?

New Zealand is somewhat a laggard in aquaculture. We got off to a late start and a government-instituted moratorium in the 2000s stalled investment. The idea was to stop and think about kind of fish farming we wanted, do some precautionary work into the risks. The delay was hugely frustrating to pioneers who could see the potential for this sustainable meat alternative.

As a result, we have a small industry but it’s growing apace (7% per year), has a global following and a clear strategy. The ambition is to create a uniquely sustainable industry that will grow from $600m now to $1 billion by 2025 and $3 billion by 2035.

The sector reminds me of the wine industry 20 years ago. It’s emergent, with innovations and cool scientists, and industry leaders working collectively and with government to set standards and a direction. Done right, New Zealand aquaculture has the opportunity to be globally distinct with unique approaches to management (such as moveable open-ocean farms) and the introduction of native species not found elsewhere. Unlike wine 20 years ago, it has the added dimension of extensive iwi involvement and a commitment to an integrated Te Ao Maori worldview. I think aquaculture’s at exciting stage. This slightly schmalzy video captures the ethos.



New Zealand farms three species: mussels, king (chinook) salmon and oysters. Because we started late, and have a heap-ton of government oversight and control, the sector looks at first blush to be much more sustainable compared to overseas. There are some high-profile problems. King Salmon had its requests for expansion knocked back after a long battle in the Environment Court due to its perceived impact on the Marlborough Sounds. This follows a decision to withdraw other expansion plans for similar concerns.

The industry  claims to be the one of the most sustainable sources of protein in the world and there’s some evidence that’s true.  All three species get the ‘Best Category’ in the Seafood Watch, by the global sustainable seafood authority Monterey Bay Aquarium.

A study last month by credible outfit ThinkStep found that ‘the impact of farmed shellfish (from farming to domestic retail stage) is comparable to tofu and their carbon footprint is comparable to or lower than all other forms of animal protein considered by the referenced study, including overseas-produced beef, poultry, dairy and eggs.’

We all know the benefits of mussels as filters of the ocean (but if you don’t check this out).

And the industry is setting standards through a compliance standard called A+:

A+ objectives align with those of world leading accredited certification programmes – such as Aquaculture Stewardship Council (ASC) and Best Aquaculture Practice (BAP). This association further substantiates the importance we place on our role of being outstanding guardians of our place and people. The A+ Programme focuses on the following areas:

  • Healthy ecology

  • Clean clear water quality

  • Responsible waste management

  • Efficient use of resources

  • Guarantee of food safety

  • Valuing Iwi participation

  • Enhancing our communities

Blue economy

The most exciting thing about New Zealand aquaculture is what’s yet to be done. When you include the 200km limit New Zealand is mostly ocean. A blue economy is emerging.

Just take one example. In 2018, the global seaweed sector was valued at more than US$13 billion, and grew 8% from 2016 to 2018. Global seaweed production has more than doubled in the last 20 years, exceeding natural supply – now more than 30% of global aquaculture production volume is seaweed. A study published last month suggests ‘growth of seaweed aquaculture would allow the scale of the seaweed industry to increase without placing pressure on wild populations and provide greater control over the consistency and quality of the product.’

The industry could yield massive benefits for New Zealand, according to the Cawthron Institute.

There are many other areas of growth. There’s research into trevally as a farmed fish, fish farms that move in the open ocean, and bio-medical extensions using farmed seafood by-products. The government has a whole oceans research programme that’s part of the National Science Challenges.

Damian Moran, a scientist with Plant & Food, says the oceans remain largely unknown for their farming potential. “Think about the number of species used in agriculture, it’s about five or six: cows, sheep, pigs, chickens, goats and so on. Compare that to the oceans, many thousands of species are yet to be explored for their potential, whether that’s as food or other uses. It’s a very open field.”

The search for the ultimate sustainable seafood continues. I think I’m getting closer.

This is the third article in a series. If you think Vincent needs to correct something (unlikely) or you have more to add, comment below or drop him a line





About the Author

Vincent Heeringa

Hi, I'm Vincent! I'm a co-founder of The Feed, a writer, marketer and PR expert specialising in food, tech and sustainability. In a previous life I was publisher of Idealog, Stoppress, NZ Marketing and Good magazines and helped establish the Science Media Centre. I'm also the host of a podcast ‘This Climate Business’. When I'm not burning the midnight oil, I'm hitting the town or planting trees with my wife Sarah. Ping me to talk about all things food. @vheeringa

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