Aquaculture – a growth sector
Food from ponds and cages
The importance of aquaculture has increased massively over the past 20 years. In 2000, just a quarter of all fishery products came from aquaculture facilities; today it is almost half. This makes aquaculture the fastest growing food production sector. In 2018, according to the FAO, 114.5 million tonnes of fish, seaweed and seafood with a market value of USD 263.6 billion were produced in aquaculture systems around the world – more than ever before. Aquatic animals accounted for 82.1 million tonnes; seaweed production totalled 32.4 million tonnes.
Roughly two thirds of the fish, crabs, mussels and other aquatic organisms farmed worldwide came from lakes, ponds or land-based freshwater aquaculture facilities. Coastal and marine aquaculture, which includes saltwater ponds along the coast and cages in coastal waters, produced a total of 30.8 million tonnes of animals in 2018. The majority of these were mussels (56.2 per cent; 17.3 million tonnes). The total amount of finfish farmed at sea was 7.3 million tonnes, while crustacean production totalled 5.7 million tonnes.
Increases of this magnitude have raised hopes worldwide that fish farming and seafood cultivation in aquaculture systems could be a solution to the problem of ensuring a continued supply of sufficient quantities of animal protein to a growing world population – and at a significantly lower resource use and lower greenhouse gas emissions than terrestrial livestock farming. Unlike pigs, cattle or goats, fish do not use energy to generate body heat. Instead, a large part of the calories ingested through feed is channelled directly into growth, which is why it is possible to produce significantly more fish meat than beef, pork or goat meat with the same feed input.
According to optimistic calculations, less than 0.015 per cent of the oceans’ surface area could produce as much fish in aquaculture as the currently landed wild catch. If, for the moment, we disregard areas of conservation concern such as coral reefs as well as possible social, environmental and economic concerns, fish farming would theoretically be feasible on more than 11.4 million square kilometres of ocean; mussels could be grown on more than 1.5 million square kilometres, biologists specializing in aquaculture argue. If all this area were actually used, it would be possible to produce an estimated 15 billion tonnes of fish per year – almost 100 times more than the amount of fish and seafood people currently consume annually.
- 3.22 > Aquaculture fish farming is a business with growth potential, as this comparison shows. If all the world’s coastal countries utilized one per cent of their suitable coastal waters for sustainable fish farming, production volumes would multiply in most countries, with the exception of China and Norway, both of which already produce more farmed fish at sea, which indicates either intensive aquaculture methods or a greater utilized ocean area.
- Other scientists, however, are sceptical of both the rates of increase and the growth potential of aquaculture. In their view, the increases to date in the FAO aquaculture statistics come mainly from domestic fish farming in China, whose figures are considered highly questionable and represent provincial planning targets rather than actual production. If the statistics were adjusted, they argue, it would be evident that marine aquaculture had reached its zenith and freshwater aquaculture was hardly growing at all. In order to be able to use fish and seafood sustainably as a source of protein for many people in the future, the primary goal should rather be to manage marine fisheries in a long-term sustainable manner. Instead, however, so these scientists note, misinformed politicians are focusing on aquaculture expansion, which in certain areas is actually detrimental to food security. For example, wild-caught edible fish such as anchovy, sprat, herring or mackerel are largely not consumed directly, but are processed into fish feed for salmon and other predatory farmed fish. The mass of wild-caught fish input is greater by far than the mass of fish output sold for human consumption, the critics say.
Proponents of aquaculture counter that criticism of adverse aquaculture practices is justified and important. It should not however result in positive projects being discredited and policy-makers becoming overly cautious of new aquaculture approaches. In overfished regions such as the Baltic Sea, sustainable aquaculture could help to improve the situation of both fishers and wild stocks in the long term.
- But it is also a fact that less than a third of the farmed fish and aquatic invertebrates are now raised without supplementary feed. This means that their share has dropped significantly over the past 20 years, although the total mass of animals reared without supplementary feed has increased to 25 million tonnes. At the turn of the millennium, 43.9 per cent of all farmed aquatic animals were raised without supplementary feed. Their share has now dropped to 30.5 per cent, the majority of which are mussels, which filter feed from seawater or brackish water.
The farming of fish, mussels and crustaceans in marine aquaculture facilities or coastal saltwater ponds is now practised around the globe. The three largest marine fish producers are China, Norway and Indonesia. Together, they produced more finfish (3.8 million tonnes) in 2018 than the entire rest of the world (3.6 million tonnes). Marine crab and crustacean farming is dominated by China, Indonesia and Vietnam. Marine shellfish farming however is almost exclusively in Chinese hands. The People’s Republic produced approximately 14.4 million tonnes of marine shellfish in 2018, almost seven times more than the rest of the world combined.
- 3.23 > Seaweed farmers in the Solomon Islands bring freshly harvested macroalgae ashore. The cultivation of plants in the sea is hard physical work and for many coastal inhabitants it is their only source of income.
The future belongs to macroalgae
China is also the leading producer of macroalgae and seaweeds, the global harvest of which has almost tripled in the past 20 years. Seaweed farming is thus the fastest growing aquaculture sector. In 2000, 10.6 million tonnes of macroalgae and seaweed were harvested. By the reporting year 2018, seaweed farmers, mainly based in East and South East Asia, were already producing as much as 32.4 million tonnes. More than 85 per cent of this production originated in China and Indonesia alone.
Two of the seaweed farmers’ best-sellers are the tropical seaweed species Kappaphycus alvarezii and Eucheuma spp., from which carrageenan is extracted, a thermally stable gelling and thickening agent used in the food and cosmetics industries, for example in the production of vegetarian bread spreads. In the European Union, it is authorized as a food additive and thickener under the food additive number E 407. Other farmed aquatic macroalgae, such as the Japanese brown algae Laminaria japonica or the kelp species wakame (Undaria pinnatifida), are sold directly as food and served in Asian cuisine, for example as an ingredient in soups. Production residues or low-quality algae are usually not disposed of, but used as a feed in mussel farming, among other things – an important step on the way to closed nutrient cycles and greater sustainability.
Since macroalgae and seaweeds are very rich in nutrients and do not require fertilizers or feeds that could pollute coastal waters, their cultivation is considered an environmentally friendly method of food production. For this reason, producers in other regions of the world are now also showing interest in seaweed farming. However, in order to reduce the food sector’s ecological footprint, large-scale algae production would have to undergo a massive level of expansion. Scientists have calculated such a scenario: If humanity were to pursue the goal of producing only one per cent of all food from algae, 147 times more algae would have to be grown for human consumption than is currently the case.
Similar or even greater quantities would be needed if macroalgae were put to additional uses. For example, there are discussions as to the conditions required for the production of bioethanol and biomethane from red and brown algae. Both products could potentially replace fossil resources. Moreover, some of the algae contain Omega-3 fatty acids and could therefore be used as fishmeal or fish oil substitutes in aquaculture facilities. Studies in ruminant livestock husbandry have shown that macroalgae fed to cattle reduce their methane emissions. And when applied to the land as fertilizer, they increase the soil’s nutrient levels.
- 3.24 > Giant kelp (Macrocystis pyrifera) forms dense kelp forests off the Pacific coast of North America. The brown algae grow to a length of up to 45 metres, making it the world’s largest bottom-anchored marine organism.
- Even more frequently, however, algae cultivation is now being discussed with regard to the creation of natural long-term sinks for large quantities of atmospheric carbon dioxide. The world’s naturally occurring macroalgae forests (also called kelp forests) sequester about 1.5 billion tonnes of carbon per year through photosynthesis. Just over one tenth of this, an estimated 173 million tonnes, is stored locally in the sea floor or transported to the deep sea and thus removed from the Earth’s carbon cycle. In this way, the kelp forests make an important contribution to reducing the carbon dioxide concentration in ocean waters and in the atmosphere.
The climate mitigation potential of the algae farmed in aquaculture systems so far is rather low in comparison. For example, if all the farmed macroalgae harvested in 2014 (total quantity: 27.3 million tonnes) had not been processed but instead disposed of in the deep sea, only 0.68 million tonnes of carbon would have been removed from the system, i.e. only 0.4 per cent of the natural kelp forests’ carbon sequestration service. On the other hand, a study by US scientists found that 48 million square kilometres of the ocean is suitable for the industrial cultivation of macroalgae. This corresponds to about five times the area of the USA. According to the researchers, using these waters fully for seaweed cultivation would probably fail due to the effort and costs involved. At a regional level, however, the cultivation of macroalgae can make perfect sense as a means of carbon sequestration and storage, especially since the macroalgae also contribute to lowering the water’s pH value and increasing its oxygen content during their growth, as long as the algae do not die off and become decomposed by microorganisms.
However, in the long term more intensive seaweed farming alone will not be enough to stop global warming. While the world’s kelp forests remove roughly 173 million tonnes of carbon from the Earth’s climate system every year, humans added around ten billion tonnes by burning coal, oil and gas in 2019 alone. The kelp forests would need around 60 years to absorb and store this much CO2. Nevertheless, it is important to make better use of the enormous potential of seaweed cultivation. Appropriately planned and implemented, large-scale seaweed cultivation could help protect the climate, improve food security, open up new sustainable sources of raw materials and improve conditions for marine organisms.
Fishmeal and fish oil
Fishmeal is a protein-containing, flour-like product that is produced by drying and then finely grinding whole fish or fish offal. In contrast, for the production of fish oil, cooked fish is pressed and the emerging liquid is separated into different components.The dark side of aquaculture
The expansion and intensification of aquaculture in coastal waters poses a number of threats to marine ecosystems, especially when it comes to animal-based aquaculture. In South East Asia, for example, around 100,000 hectares of valuable mangrove forests were cleared between 2000 and 2012. Almost one third of the forest had to give way to the creation of coastal shrimp aquaculture ponds. In Indonesia, the proportion of mangroves cleared for aquaculture was almost 50 per cent. In the same regions, many stretches of coastline had already been transformed in the 1990s with a view to the expansion of shrimp farming, which brings in foreign currency. As a result, wild-caught tropical shrimp declined, and local coastal fishermen landed less fish because the mangrove forests – the natural nursery grounds for juvenile shrimp and fish – were gone.
Furthermore, the significant area lost to coastal aquaculture is only one problem of many. The feed used in such facilities still partly consists of fishmeal and fish oil. For its production, small schooling fish such as the Peruvian anchoveta (Engraulis ringens) or the Atlantic herring (Clupea harengus) are overfished worldwide. According to the FAO, approximately 18 million tonnes of fish caught were processed into animal feed in 2018. This quantity is far lower than the peak of more than 30 million tonnes used in 1994, but also well above the low of 2014 (14 million tonnes). Critics of this practice have calculated that currently roughly 25 per cent of the schooling fish caught are processed into fishmeal or fish oil. In this way, fish that in many parts of the world are consumed especially by the poorer population are transformed into fishery products such as salmon fillets, which ultimately only the better-off in society can afford, say the critics. In their view, farmed salmon, seabass, etc. can only contribute to solving the global food problem if substitutes for fishmeal and fish oil are cheaper and used more extensively by farmers.
3.25 > For a long time, the giant tiger prawn (Penaeus monodon), also known as black tiger shrimp, was the most widely cultured prawn species in the world. It has now dropped to fourth place. Nonetheless, a total of 750,000 tonnes of this species was produced in 2018.- Excess feed in marine aquaculture installations not only pollutes fjords and coastal waters but downright over-fertilizes them. In many places this can lead to increased algal growth and also to the development of oxygen-deficient zones. For a long time, fish and shrimp farmers around the world also made unregulated use of antibiotics in order to contain diseases in the much too dense animal populations. In the shrimp ponds of South East Asia, among other regions, this resulted in the development of pathogens resistant to antimicrobials and ultimately led to several waves of severe outbreaks that destroyed large parts of the Asian shrimp production, especially stocks of the high-yielding giant tiger prawn (Penaeus monodon), also known as black tiger shrimp.
Much research has been done to curb the disease outbreaks. Instead of the giant tiger prawn, whiteleg shrimp (Litopenaeus vannamei) now predominate in South East Asian breeding ponds. Moreover, attempts to breed disease-resistant shrimp were successful, so that the use of medication has been greatly reduced. Many Norwegian salmon cages are now also home to a significant number of lumpfish. The small, greenish iridescent fish are used as cleaner fish because they prey on a parasite of salmon that occurs naturally in Norway’s fjords – known as salmon louse (Lepeophtheirus salmonis). This copepod attaches itself to the skin of the farmed fish and causes wounds that can be fatal to the salmon. But the lumpfish eat the parasites before they can do any great damage, thus eliminating the need for medication or expensive pest control. This benefits not only the salmon and the fish farm operators, but also the environment.
- 3.26 > Free-floating or anchored fish cages with remote-controlled feeding units, as tested here off the coast of Hawaii, could offer the opportunity to shift fish farming out to the open sea and reduce aquaculture’s ecological footprint in coastal waters.
- However, the only way to prevent “faunal mixing” as a result of improper aquaculture management would appear to be targeted bans on fish farming. For example, in December 2019, after a fire in an aquaculture installation off the coast of Vancouver Island, thousands of Atlantic salmon escaped into the surrounding sea, which is home to wild Pacific salmon. Marine conservationists and environmentalists now fear that the former caged animals may transmit diseases, viruses and parasites to the native Pacific salmon, with which these wild stocks cannot cope. And there is also the risk that the two species will mate and produce offspring. Researchers speak of “genetic pollution” in such cases.
Parasites introduced through aquaculture may multiply abruptly under certain circumstances and, in the worst case, impact food webs and entire ecosystems in the facilities’ wider vicinity. In polluted coastal waters there is also an increased risk of new pathogens emerging that may also be dangerous to humans, for example pathogens that cause diarrheal diseases. This risk is elevated especially in the coastal regions of India, Bangladesh and Myanmar. Despite the high population density, these regions are also home to intensive aquaculture facilities and the annually recurring monsoon rains ensure regular flooding, in the course of which pathogens can spread quickly and come into contact with people.
If one considers against this background the call for the growing global demand for fishery products to be met primarily by means of an expansion of aquaculture, it is obvious that new, efficient and, above all, resource-conserving strategies for food production at sea are needed. Hope is offered by approaches that focus on the entire ecosystem, both in aquaculture and in fisheries.
Progress and innovation in aquaculture
The severe ecological consequences of intensive marine and coastal aquaculture (especially when it comes to fed production systems) have prompted science and industry to search for new, more environmentally friendly methods and technologies. Notable progress has been made in several areas, such as in species selection, feed composition and the development of integrated circular systems.
More than 600 species of fish, crustaceans and mussels are currently farmed in aquaculture systems around the world. A notable positive development is the fact that increasingly native species are farmed in the respective regions. In Europe, for example, these are sea bass (Dicentrarchus labrax), gilt-head bream (Sparus aurata) and turbot (Scophthalmus maximus). All three species are being produced in increasing quantities. In the tropics, the same is true for species such as barramundi (Lates calcarifer) and groupers (Serranidae) as well as for Rachycentron canadum – a spiny relative of the mackerel – known as cobia, black kingfish or black bonito. Both cobia and groupers like warm water. Both species grow quickly and are very well suited for aquaculture production. Moreover, their meat quality is very good, so producers are hoping for high production volumes and good sales prospects.
- Intensive aquaculture research and rising world market prices for fishmeal and fish oil have resulted in a significant reduction in the proportion at which these components have been added to aquaculture feeds over the past two decades. In the past, feed for predatory fish such as salmon or sea bass consisted mainly of animal products. Nowadays grains, oilseed crops or legumes substitute these animal products to such a degree that the proportion of fishmeal in feeds for trout and salmon, for example, has fallen to ten per cent or less. This proportion could be further reduced if it were possible to cost-effectively produce microalgae in such large quantities that they could replace fish oil. Similar to fish oil, microalgae contain omega-3 fatty acids, which are indispensable for fish health and are one of the reasons why fish is so nutritious for humans.
When asked how freshwater consumption can be reduced in circular land-based systems, aquaculture researchers have taken their cues from aquariums for ornamental fish and developed purification systems that filter out and convert the excreta of the fish. In this way, it is possible to produce one kilogram of fish with less than 100 litres of fresh water. For comparison: in conventional pond or flow-through processes, 2000 to 200,000 litres of water were needed up to now to produce the same quantity of fish. Scientists have also developed water treatment systems and management instructions that can reduce the adverse impacts on the water used in these widely employed conventional systems.
- The model of a closed nutrient cycle was the inspiration for the development of new Integrated Multi-Trophic Aquaculture (IMTA) systems, in which selected species from different levels of the food web are kept in such a way that the excreta of one species serve as fertilizer or feed for the next species and are used as effectively as possible by the latter. An example would be a facility where fish are kept alongside mussels, macroalgae and crustaceans. Feed is only used at the start of the chain, in the form of fish food. The fish faeces are then filtered out of the water by the mussels and algae which utilize them as a source of nutrients. Meanwhile, the crustaceans on the sea floor consume what is left over from the production of fish and mussels and sinks to the bottom.
The advantages of such systems are obvious: While surplus nutrients are prevented from entering coastal seas as a result of the facilities’ operation, the operators’ economic risk is also reduced as the parallel production of different species within a single system reduces the production costs per species. Moreover, the producers can market a wider range of products which makes them more resilient to short-term fluctuations in demand and prices. Taking into account the customers’ increasing awareness of sustainably produced foods, it is likely that fishery products from integrated aquaculture facilities will be purchased more often than products from less sustainable production and that the operation of such facilities will enjoy greater acceptance by the local population.
Researchers are still conducting experiments on the most beneficial combinations of species for specific regions. However, in the tropical regions it is becoming apparent that integrated aquaculture systems could be an elegant solution for the urgently needed production increases in marine aquaculture. While most of the research in this regard is being undertaken in South East Asia, intensive work is also ongoing in Canada, Chile, Israel and South Africa.
Regionally adapted solutions
A switch from conventional aquaculture to integrated systems will not suffice everywhere. Especially where natural coastal ecosystems have suffered enormously from intensive use in the past, the dismantling of existing aquaculture installations will also have to be considered if damaged coastal areas are to be revitalized. The example of the Chinese coastal metropolis of Xiamen shows just how comprehensive such a restoration endeavour needs to be. Until 2002, the entire coastal waters of this port city with its 5.1 million inhabitants were devoted to aquaculture. For more than two decades, muck from the ponds and the residues of the intensive use of feed in fish cage installations polluted the bay on which the city is located. In the period of 1984 to 1996, this pollution contributed to major fish kills which occurred roughly twice a year. The mangrove forest died off almost completely and populations of seabirds and river dolphins experienced dramatic declines.
The city then initiated a new four-stage marine and coastal management plan to turn the situation around. The aquaculture installations were completely dismantled, the local mangrove forest was replanted, wetlands were renaturalized, wastewater treatment plants were built and walls and embankments hampering water exchange were demolished, to name just a few of the measures as part of the comprehensive programme. According to scientists the results are impressive: Water quality in the bay has improved so much that there are renewed prospects for herons, river dolphins and many other species.
However, the radical dismantling of aquaculture installations is a feasible solution only in exceptional cases. The complete decommissioning of facilities is contraindicated by the growing global demand for fishery products. If we want to continue to meet this demand in the future, the FAO believes that this will only be possible if even more animal and plant products are produced in aquaculture systems. Moreover, in many coastal regions and areas, marine food production is the only source of income for the local population. The closure of aquaculture facilities would deprive many people of their livelihoods, especially in the tropics.
- Highly divergent approaches to the future of aquaculture are being discussed in the scientific community. Some experts recommend a focus on class, not mass. They favour the operation of individual integrated facilities distributed over a large area so that their ecological footprint is as small as possible. But these facilities should then produce high-quality products and market them at an appropriate price.
Other scientists advocate an expansion of global aquaculture, premised on avoiding both environmental damage and conflicts with indigenous populations. Their suggestions include the following:
- define and enforce environmental standards;
- plan the location of new aquaculture installations on the basis of scientific information and in consultation with other local marine user groups;
- introduce certificates or label schemes for sustainable aquaculture production and make supply chains transparent;
- intensify the farming of non-fed species;
- in the case of fed species, further optimize feed ration formulation and feed use;
- find alternatives to marine mass fish farming in net cages – for example, by creating synergies through the conversion of such systems to integrated systems with farmed fish, cleaner fish, algae and mussels;
- reduce susceptibility to disease through breeding and genetic modification;
- shift production to the open sea to reduce the burden on coastal waters;
- stake efforts on ecosystem-based husbandry systems, in coastal areas as well as in the open sea.
- Each of these ideas has its benefits. However, for every pro there is also a con when it comes to implementation. It is often argued that many of the proposed measures are too expensive and thus uneconomical for operators of aquaculture facilities. To the disappointment of aquaculture researchers, there have hardly been any field trials that yielded strong figures to refute this argumentation. Calculations of the economic viability of sustainable aquaculture approaches are mostly based on computer modelling.
But the fact is that if aquaculture is to be practised in harmony with nature, there cannot be just one blanket approach. Instead, it is essential that the methods used are adapted to local and regional conditions. It is upon policy-makers to define and introduce the laws and regulations that will resolve the often unclear issues of ownership and liability, provide attractive incentives for the sustainable operation of facilities (such as tax benefits, subsidies, etc.) and prescribe methods and threshold values for the effective environmental monitoring of aquaculture operations.
Scientists argue that in countries where there are no clear rights, regulations and responsibilities, operators of aquaculture facilities have no reason to invest in sustainable technologies and feed research. If aquaculture were to be expanded in such contexts, it could reasonably be expected that water quality would rapidly decline, that the marine environment would be severely damaged and that the health risk for coastal residents would increase. The decision as to whether and how to expand aquaculture is therefore not an easy one. Costs and benefits would need to be weighed carefully.
Certification marks for responsible aquaculture
A variety of certification marks allow customers who wish to buy fish and seafood from responsible or sustainable aquaculture systems to recognize such products. Based on the sustainability label of the Marine Stewardship Council (MSC) for wild-caught seafood, there is also a quality label for socially and ecologically sustainable aquaculture – that of the Aquaculture Stewardship Council (ASC). The ASC has developed aquaculture standards for 17 species groups whose market value is high and the production of which has far-reaching impacts on the environment. These farmed species include marine animals such as abalone, venus clam, common mussel, oyster and scallop, as well as salmon, sea bass, gilt-head bream, stone bass and cobia. Since November 2017, there has also been a joint ASC-MSC standard for seaweed cultivation. In the course of the ASC certification process, plant operators are motivated to:
- use fewer pesticides, chemicals and antibiotics;
- reduce water pollution;
- feed more efficiently and thereby prevent eutrophication of facilities and coastal waters;
- implement technical upgrades to their facilities to prevent farmed fish from escaping;
- treat all employees fairly and in accordance with appropriate social standards;
- interact in a positive way with the local communities in the facilities’ surroundings.
- In addition, participating aquaculture companies must ensure that their supply chains are designed in such a way that they exclude any possibility of erroneous substitution or admixture of certified and non-certified fish and that each product can be reliably traced back from the point of sale to the aquaculture facility from which it originates. By the end of 2019, the ASC had certified more than 1100 aquaculture facilities in 42 countries. Together, they produced almost two million tonnes of fish and seafood. Compared to 2014, the number of participating farms had increased by 450 per cent and the amount of fishery products produced according to ASC standards had increased by 181 per cent. The environmental requirements imposed by the ASC are also having an effect: certified shrimp farms in Vietnam, for example, were able to halve their adverse environmental impact through improved waste management. ASC salmon farms reduced their reliance on fishmeal from wild catches by three per cent. The certification guidelines for aquaculture facilities that bear the German Naturland label for certified organic aquaculture are stricter than the ASC standards. Operators undertake, among other things, to:
- adhere to species-appropriate husbandry conditions and low stocking densities;
- use certified organic feed, the fishmeal and fish oil content of which originates from residues from the processing of culinary fish and not from industrial fisheries specifically exploited for feed production;
- refrain from the use of genetic engineering, chemical additives, growth promoters and hormones;
- comply with strict regulations on the use of medication (e.g. the use of antibiotics is prohibited in shrimp farming);
- provide high social standards for their employees.
While environmental organizations such as Greenpeace welcome the Regulation in principle, they also describe the rules as the lowest common denominator. Important criteria are not sufficiently strict in their view, with most stocking rates, for example, being set too high and hazardous chemicals having been approved for use. Critics note that the EU Regulation thus falls far short of the standards that the Naturland association, for example, has been setting for more than a decade.