fish swimming in a school

Aquaculture for fish consumption | The shocking truth about Friday’s fish

Demand and the nutritional benefits of fish have produced a phenomenal rise in aquaculture for fish consumption. Is fish farming the answer to sustainable seafood?

The dramatic rise in aquaculture for fish consumption is no surprise. 

Fish are perfect parcels of nutrient-dense food, and humans have a long relationship with fish as a food source and with the habitats where fish live. We have always been keen on a seafood platter and have risked life and limb to secure fish supplies—it takes courage to work on a trawler at night on an angry sea.

Given that humans are smart, innovative and can sniff an economic opportunity from a thousand yards, the rise of aquaculture—the breeding, raising, and harvesting of fish, shellfish, and aquatic plants—is no surprise either. 

People farm on land for subsistence and profit, so why not farm in the water?

Aquaculture for fish consumption is safer, controllable and more reliable than the increasingly fickle catch from wild fish stocks. And there is demand from consumers, rich and poor alike, who recognize the nutritional value of fish.

All good. 

But the truth is that the production curve from aquaculture cannot keep rising forever. 

Fish on Friday

Christians are supposed to fast on the sixth day of the week, a Friday. 

Back in the day, fish was the food of the poor people, so on the sixth day, the wealthy would kid themselves that they were roughing it and meet the requirement to fast by eating fish on Friday.

Fish and chips on Friday is still a thing in Britain, although in 1985, the Catholic Church in England and Wales allowed Catholics to substitute another form of penance instead of fasting or fish. Maybe they did without ice cream for dessert.

Fish make for excellent nutrition, being low in fat and a high-quality protein filled with omega-3 fatty acids and vitamins such as D and B2 (riboflavin). Fish is also rich in calcium and phosphorus and is an excellent source of minerals such as iron, zinc, iodine, magnesium, and potassium—no wonder the poor survived on it.

Not strictly fasting then, but hey.

When I was born in 1961, the global average fish consumption in the UK was 19.8 kg per person per year. The average global John Doe ate 12.7 kg in the year. 

By 2017 the UK folk were still tucking into fish and chips but at a similar rate to when I was a kid, 19.7 kg. Meanwhile, the global John munched almost double at 21.4 kg a-1.

The rich kept to their fish on Friday, and the poor—half the global population lives on less than $10 a day—ate a lot more.

infographic of the amount of fish eaten in 1961 compared to 2015

In 1961 the total fish eaten was roughly 36 million tons, and 94% was wild-caught. The oceans, lakes and rivers coughed up the catch.

In 2015 it was 200 million tons only the oceans and lakes were at their limit once extraction was at thoroughly 90 million tons. The rest had to come from somewhere else. 

This occurred through an exponential increase in aquaculture for fish consumption—rearing aquatic animals or cultivating aquatic plants for food. 

Since 2012, humans have grown over half the tonnage of fish consumed.

Aquaculture became popular as the wild catch declined and especially since that catch plateaued in the 1990s. The demand for fish was rising, but the wild-caught supply needed help to keep up, despite the technology and vast fishing fleets. 

Businesses saw the opportunity and met the need through various forms of aquaculture for fish consumption. The rise in seafood production from aquaculture is remarkable.

graph of the increase in aquaculture for fish consumption increasing exponentially since 1960

Aquaculture for fish consumption is important

Fish year-round for consumers, incomes for producers, and reduced pressure on wild fish stocks are all good. 

Aquaculture can also provide ecosystem services in the form of wastewater treatment, bioremediation, habitat structure, and the rebuilding of depleted wild populations through stock enhancement and sprat dispersal

Freshwater fish comprise the majority of aquaculture production today. These fish are raised in ponds, lakes, canals, cages, and tanks and benefit from various inputs, technology, and management. 

Farmed fish and shellfish species are cold-blooded and physically supported by water. They are more efficient feed converters and have higher edible yields than most terrestrial animals. Over two-thirds of aquaculture production in 2012 relied on supplemental feed inputs. And this food has to come from either food-quality and human-inedible coproducts from the crop, livestock, and fisheries sectors grown on land or harvested from the ocean, lakes and rivers. 

However attractive farmed fish are as a food source, they are still animals and must be fed. Farmers feed fish to fish but also use a lot of soybeans and maize. Aquaculture relies on crop-based feeds and also fishmeal and fish oil. But fish food is a small proportion (∼4%) of industrially produced global animal feed.

Farmed fish’s price is relatively stable globally compared to other food types, especially cereals and oils. This is a good thing, significantly, because price spikes in wheat, rice and corn harm the poor. 

Whilst the spikes from weather-related production failures are less likely in aquaculture, fish prices track those of crops and have risen since the early 2000s.

graph of the price index for food and aquaculture showing volatility from year to year and an increase since 2000

Data from Troell, M., Naylor, R. L., Metian, M., Beveridge, M., Tyedmers, P. H., Folke, C., … & De Zeeuw, A. (2014). Does aquaculture add resilience to the global food system?. Proceedings of the National Academy of Sciences, 111(37), 13257-13263.

What aquaculture has done is to buffer the global demand for fish from the plateau in production from capture fisheries. We now farm a lot of fish because far fewer fish are left in the seas, oceans, and lakes.

But it is not all fish and chips on Friday.

Fish might still be the food of the poor, but there are now as many people living on less than $10 a day than were alive in total in 1961. Many of these people rely on nutrient-dense meals any day of the week.

And then, there are the production challenges and externalities.

Aquaculture is not a panacea

Aquaculture comes with most of the general problems and consequences of agricultural intensification—energy, nutrient and pesticide inputs, mechanisation, sustainability—as well as a few of its own:

  • pollution, especially nitrate leaks
  • coastal habitat loss
  • potential disease and parasite transmission between farmed and wild fish populations introduction and spread of invasive species
  • appropriation of freshwater resources
  • depletion of wild fish populations to stock aquaculture operations 
  • overfishing of wild fish populations used as ingredients in aquaculture feeds

The use of wild fish in aquafeeds can also have food security implications for low-income households, particularly in sub-Saharan Africa and parts of Asia and Latin America, that depend on low-trophic level fish as a critical constituent of their diets.

In short, aquaculture for fish consumption is an input-output system like intensive farming on land. Fish farmers apply inputs to ensure the system can produce fish. 

Intensification leverages food ecology into a form of industrial production. Good for profit but one that requires inputs of energy and nutrients. And those inputs have to come from somewhere. Unlike wild-caught fish, farmed fish do not just appear in nets. They have to be fed and looked after. 

And like many industrial processes on land, there is waste

Some of these are obvious and direct pollution events, like the leaks of nitrate from fish pens, but there are other externalities—consequences of production that appear outside of the supply chain, such as the loss of habitat and depletion of wild fish populations.

infrastructure of a fish farm in an estuary with hills in the background

Many fish farms are built in estuaries for easy access and water flow with the tides. Photo by Lucut Razvan on Unsplash

The bottom line of aquaculture for fish consumption

Aquaculture for fish consumption is essential to the 22 trillion kilocalories daily to feed everyone well.

Wild-caught fish cannot feed the 8 billion people we already have, plus the extra 8,000 an hour from the population spike. Aquaculture is essential to meet the shortfall in demand.

But that demand is huge.

If the 8,000 new arrivals in the last hour ate the average amount of fish per person per year (21 kg), then for each hour of every day, 24/7, we need an additional 168 tonnes of fish per annum.

I can’t present the answer to the multiplication for the new people each day or month or year; the numbers are incomprehensible.

What sustainably FED suggests

Everywhere on this website, you will see references to the human diet. 

We are designed for hunting, gathering and digesting various food types, from prawns to papaya. It has contributed to our widespread success. Our omnivory gives us flexibility and adaptability.

Humans are also large mammals with an evolved physiology designed to process nutrient and energy-dense food. 

Elephants are big mammals too. They use their size to forage widely and consume vast amounts of relatively nutrient-poor foods, primarily grasses, leaves and even bark at a push—they have a high throughput strategy, meaning they are eating most of their waking hours.

Humans went the other way. We take infrequent meals and hold onto our food to digest it thoroughly. We could only be successful in this strategy with foods high in nutrients and energy. Feeding everyone well means supplying at least some of those high-density nutrient meals.

Throughout recorded and pre-history, humans have found fish, shellfish, and aquatic plants from rivers, lakes and the ocean to make a good meal. We will always be keen on Friday’s fish.

The shocking truth about aquaculture for fish consumption is that farming fish can quickly go the way of industrial farming on land. It can become over-reliant on inputs, especially energy, and avoid its externalities.

Aquaculture for fish consumption is not sustainable, just like the current wild fish catch.

Fish and chips, anyone?

Hero image from photo by kate on Unsplash


Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

Add comment

Subscribe to our explainer series

* indicates required

Most discussed