According to a United Nations report, the world’s population is estimated to grow to 8.5 billion people by 2030, and reach 9.7 billion people by 2050. One of the biggest concerns regarding this rapid population expansion is sustainable food security. Aquaculture, the fastest growing food production sector, could be one such way to ensure this. As of 2016, more seafood is sourced through aquafarming than is being caught in the wild. Aquafarms are uniquely positioned to address the growing demand for seafood protein. However, as they continue to become more prevalent, the need to ensure that their sustainable development also increases. 

What is Aquafarming?

Aquafarming, also known as aquaculture, is the farming of aquatic organisms, such as fish, crustaceans, molluscs and plants. Aquafarming can occur in both marine and freshwater environments. There are numerous aquafarming methods, but most follow the same basic production chain. Beginning at a hatchery, a combination of a laboratory and a farm, the fish are spawned, hatched and cared for until they are large enough to move to the next stage; the farm. The fish remain on the farm where they are fed by food produced at farm mills (another stage of the production chain) until they are ready to be harvested. Once they have reached harvest size, the fish are transported to processors where they are packaged and sent to food retailers. The exact details of the farm-to-table method vary based on species and location. Some farmers choose to farm their fish in net pens or cages in water. This method is sometimes referred to as ‘cage cultures’. These enclosed cages need to be carefully monitored to ensure that they do not harm the surrounding ecosystems. Marine shellfish can be ‘seeded’ on the seafloor, grown in bottom cages, or grown in floating cages. 

Farmers that are farming freshwater fish, or who don’t have access to oceans or estuaries, use ‘pond cultures’. Here the fish are kept in earthen ponds or tanks on land. Ensuring that the fish have continuously filtered and oxygenated water is especially important in these systems. Two ways to ensure this are recirculating systems and integrated multi-trophic aquaculture systems. In recirculating systems, the fish, shellfish and/or plant-life are farmed in ‘closed-loop’ systems that continuously filter the water and recycle waste. In an integrated multi-trophic aquaculture system, several species are farmed in one system, so that the waste or by-products of one species serve as food for another. 

The Benefits of Aquafarming 

According to another UN report, since 1961, the annual increase in fish consumption has been double the population growth of people. To meet this growing demand, the seafood industry will need to increase production by over 1.6 million tons each year. This demand can no longer be sustained by ocean fishing, as many fish stocks are on the brink of collapse from overfishing. Aquafarming is able to bridge the widening gap between seafood supply and demand. 

One of the major advantages of aquafarming over agriculture is that fish require far fewer calories than cows, pigs or sheep. The reason for this is two-fold. Firstly, fish are coldblooded, meaning they don’t expend energy maintaining their own body temperatures. Secondly, fish live in a buoyant environment, so they use less energy fighting gravity than terrestrial animals do. In order to produce one pound of body mass respectively, a cattle farmer will need approximately 6.8 pounds of feed, a chicken farmer will need approximately 1.7 pounds of feed, while a salmon farmer will need approximately 1.1 pounds of feed (this varies between different species). These ratios suggest that farming salmon is almost seven times more efficient than farming beef. 

While most commonly associated with fish farming, aquafarming also involves the farming of shellfish, molluscs and marine plants. A common belief in the sustainability community is that, in order to ensure global food security, people will need to learn to eat further down the food chain more regularly. Shellfish are considered to be one-step up from the bottom of the food chain. They are high in nutrients and omega-3s and low in fats, making them a healthy protein. Shellfish filter excess nutrients (such as nitrogen) which makes more oxygen available for other species. They also feed on phytoplankton (microscopic plankton) which allows more sunlight to reach the ocean floor, as the presence of phytoplankton can physically prevent sunlight from reaching the ocean floor; this in turn increases aquatic vegetation. 

Marine oyster farms have been found to hold more biodiversity than the adjacent wild water. As these farms can be grown in otherwise uninhabited areas, the increased biodiversity within the farms can positively impact the surrounding waters. Another food source that aquafarming can produce is kelp, a nutritious vegetable that is particularly popular in Chinese and Japanese cuisines. The kelp industry in East Asia alone is a USD$5billion industry. Certain species of kelp can grow at incredibly fast rates, some as much as 12cm a day. Kelp farms can be successfully sustained without freshwater, arable land, pesticides or fertilisers. This, coupled with their fast growth rates, make kelp farms more efficient and environmentally friendly than many traditionally grown terrestrial vegetables.  

Aquafarming is particularly important in developing countries, where it both directly and indirectly affects food security. It directly affects food security through the increase of food availability and accessibility, producing a relatively healthy and affordable protein source. Fish is important for developing countries because it contains many of the vitamins and minerals that combat some of the most prevalent and severe nutritional deficiencies. Fish have high fertility rates and low feed conversion ratios, making it a more biologically efficient food source than terrestrial livestock. 

The UN estimates that over 100 million people rely on aquafarming for their living; with the increase in aquafarming in developing countries, more people will have access to job opportunities. Aquafarming acts as a driver for economic development, and through this allows more people indirect food security, as their ability to access food is no longer hindered by economic hardship.

The negative consequences of modern agriculture have been well documented. The habitat destruction, water pollution and the food safety scares due to overcrowding and disease have cast a dark shadow over industrialised farmers. In order to sustain humanity’s growing protein consumption, several studies have suggested that a dietary shift towards sustainable seafood protein could be a solution. It is predicted that seafood consumption will increase by 27% by 2030, and that the aquafarming sector will grow by 62% in the same period. This immense growth offers significant opportunities for many people, but also highlights the need to ensure that the growth of the sector is handled in an environmentally sustainable manner.  

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Downsides of Aquafarming 

During the aquafarming boom of the 1980s, large areas of tropical mangroves were bulldozed to create space for shrimp farms. Mangroves are of critical importance to the health of coastal ecosystems as they protect shorelines from erosion, serve as nursery areas for many different species of fish and invertebrates and support a number of threatened and endangered species. While the destruction of mangroves for shrimp farms has reduced since the 1980s, it is important to ensure that the predicted expansion of the aquafarming industry does not follow in the habitat-destroying footsteps of the agricultural industry. 

A second concern regarding the expansion of aquafarming is pollution. Aquafarming pollution mostly involves nitrogen, phosphorus and dead fish. When a large number of individuals are enclosed in a confined space, their waste matter becomes concentrated. Aquafarming pollution is currently a widespread hazard in Asia, as 90% of farmed fish are farmed there. One way to mitigate the problem of concentrated waste matter is to use an integrated multi-trophic system, recycling one species waste matter as food for another. Another way is to use a recirculatory system, where the waste matter is filtered out and fresh water pumped back in. However, recirculatory systems are expensive to run, often requiring massive water treatment systems and immense amounts of electricity to keep the pumps running. This is costly both for the farmer and the environment, as land will need to be claimed for the water treatment facility and most electricity is generated from fossil fuels. Better technology needs to be developed in order to make recirculatory systems more sustainable, but as they are not one of the most popular forms of aquafarming, it is hard to foresee when/if this technology will be developed. 

As has been seen in agriculture, enclosing large numbers of individuals in a small space creates a breeding ground for bacteria and diseases. In an attempt to combat this, some Asian farmers have been using antibiotics and pesticides. Many of these antibiotics and pesticides  are banned in the US, Europe and Japan, as they are known or suspected carcinogens. It is estimated that the US, which imports 90% of its seafood, only inspects about 2% of the imports. The use of antibiotics and pesticides not only threatens the health of those that eat the fish, but can also increase the prevalence of antimicrobial resistant bacteria (AMR). In a study published in the scientific journal, Nature, scientists found that aquafarms have high levels of AMR, which causes over 35 000 deaths each year in the US alone. It is predicted that these numbers are much higher in developing countries, and that they will continue to increase with socio-economic development. Antimicrobials are often administered to fish through their feed. However, it is estimated that around 80% of these antimicrobials are dispersed into the surrounding environments where they can remain active for months. These concentrations of antimicrobials put selective pressure on bacterial communities, which causes the development of AMR. The study also found that “higher AMR levels of aquaculture-related bacteria were correlated with warmer temperatures”. As ocean temperatures continue to rise as a result of global warming and the aquafarming industry continues to grow, the need for immediate, co-ordinated international intervention to limit the use of antimicrobial drugs in aquafarming is great. 

A point of conflicting views is the effect of aquafarming on greenhouse gas emissions. According to one study, aquaculture has a much lower GHG emissions intensity than ruminant meat, and a similar emissions intensity to pork. However, the study goes on to note that the moderate emissions intensity does not justify complacency, especially as post-farm emissions were not included in the calculations. Another study found that the conversion of rice paddies into aquafarms in China was resulting in a “globally significant [rise] in CH4 emissions.”  Quantifying the effect of aquafarms on GHGs is an intricate process, but given the rapid expansion of aquafarming, it is an area that needs further investigation. 

Looking to the Future

In 2015, the Member States of the UN adopted the 2030 Agenda for Sustainable Development, which includes 17 Sustainable Development Goals (SDGs). The aim of the agenda is “to shift the world to a sustainable and resilient path that leaves no one behind.” Food and agriculture play a key role in achieving all of the 17 SDGs. Many of them are relevant to fisheries and aquafarming, no more so than SDG 14, which is to “conserve and sustainably use the oceans, seas and marine resources for sustainable development.” In order to end poverty by 2030 while mitigating degradation, food production needs to be increased in a way that ensures that practices are sustainable and non-detrimental to the environment. This needs to be the focus of the aquafarming industry moving forward. 

While the expansion of aquafarming is still in its infancy, the concept of using polycultures dates back hundreds of years. Over 1 000 years ago, Chinese farmers developed an integrated multi-trophic system that utilised manure from ducks and pigs to fertilise pond algae. The algae was grazed on by young carp in the pond. When the carp were bigger, they were caught and placed in flooded rice paddies. There they ate insects and weeds, and fertilised the rice with their excrement. Finally, when the carp had grown to a suitable size, they were eaten by the farmers. This system is still used in over seven million acres of rice paddies in China, and perhaps holds an important lesson for the future of aquafarming. In the haste to expand and capitalise on the ever-growing demand for seafood, it is important to take time to understand how the natural world maintains balance between different species, and to ensure that aquafarming policies are aligned with and respect this balance.  

Featured image by: Flickr