The stagnation of global wild fish catches is an indication of how necessary aquaculture is today. In the face of the rising world population it seems to be the only way to meet the growing demand for high quality protein. This explains the pace at which the development of aquaculture is being driven worldwide. Analogous to the "green revolution" that revolutionised agriculture in the 20th century, the term "blue revolution" is often used in the aquaculture sector. There is a high degree of diversity in almost all areas of the aquaculture industry... be it in the farming methods used, the species produced, possible farm locations, feed and feeding, or the rearing of stocking material, aspects of animal welfare and more besides. This makes it difficult for people to keep up-to-date with developments so that they can form a fair opinion without prejudice.
Concerns and reservations about aquaculture range from health and environmental issues, animal protection and welfare to risks from biological and chemical pollution. Many of these worries are based on vague rumours, long outdated production standards or hearsay. Significant improvements or the intensive efforts made by the aquaculture industry to achieve more sustainable production are hardly noticed by the public with the result that the principal advantages of aquaculture are unknown to many people. The domestication and farming of aquatic species, for example, entails less risks than the production of land animals which has had a very severe impact on human life. Almost all major infectious diseases that can spread to humans, including smallpox and diphtheria, originate in terrestrial animals. To date, not a single human pathogen with comparable virulence has been detected in aquatic animal and plant species although many more species are produced in aquaculture than in agriculture.
World aquaculture production (including aquatic plants) exceeded 110 million tonnes in 2016 with a first-sale value of more than USD 240 billion. The annual growth rate of nearly 8 per cent in the 1980s and 1990s has slowed to 5.8 per cent since the turn of the millennium but aquaculture still continues to grow faster than other food production sectors. This development has led, and indeed leads, in many places to conflicts about the use of land and water areas, fresh water, energy and other resources, and attempts are being made almost everywhere to limit the unrestrained growth of aquaculture through legal requirements and other regulations. This has increased the pressure on the sector which tries to balance its performance with a higher production intensity, and individual companies are now moving into the comparatively free offshore sector.
Verifiable facts instead of "fake news”
It will probably never be possible to fully dispel criticism and concerns about aquaculture but the general rejection the industry often faced in the past has lessened somewhat in recent times and aquaculture activities are now viewed and assessed in a more differentiated way. The reasons behind this change can be very different. Maybe it is just that people are getting used to aquaculture which has become almost commonplace. But overall public perception of the industry is also changing as it becomes increasingly clear that it is indispensable for our supply of fish and seafood. In addition, there has been progress and improvements in production. It is now more sustainable, more environmentally friendly and more animal-friendly. Aquaculture companies that play an active part in their locality, maintain close contacts with the local population, responding to their concerns and expectations and negotiating compromises together are particularly well accepted. It is usually the same or similar issues that are at stake: the use of antibiotics and chemicals, excessive nutrient input into water bodies, possible escapes competing with wild species, or the introduction of diseases and invasive species.
The media, press, TV and, in particular, the internet, play a key role in shaping public opinion. They reach almost all consumers and can report promptly on the current state of aquaculture, any successes or unsolved problems. However, this requires informed journalists with a genuine interest in developments and whose knowledge goes beyond the well-known prejudices and platitudes. Unfortunately a lot of the reports and descriptions that can be read today still draw a rather distorted picture of aquaculture and make little or no attempt to explain to consumers how fish and other aquatic organisms are actually farmed. Information about new developments and progress made is often only available to the aquaculture community and remains largely unknown to the public. This is also why some prejudices and misunderstandings about aquaculture stubbornly remain, despite the fact that they are incorrect or – thanks to modern developments – are in the meantime no longer relevant.
Although individual aquaculture enterprises can indeed endanger coastal ecosystems generalisations and oversimplifications are not justified. For example, shrimp farms are often blamed for the loss of global mangrove forests, whose area has declined by almost 20 per cent since the 1980s. According to estimates by the United Nations Environment Programme they are responsible for only a quarter of this quantity, however, i.e. only 5% of the global mangrove area. Equally large damages were caused by felling and rice cultivation, the construction of salt works, the use of mangroves as grazing land for camels and goats, oil drilling, tourism and the construction of roads and ports. Nevertheless, almost without exception, shrimp farms stand out at the top of the list as the guilty party. What is almost completely overlooked is that today hardly any new farms are established in mangroves, that many old facilities have been closed down, and that the areas have in many places been reforested.
It is also much too rarely reported that some forms of aquaculture are even beneficial to nature. The enormous filtration capacity of mussel cultures, for example, contributes greatly to improving water quality at the site. A single oyster can pump up to 50 litres of water through its body every day to filter out the plankton it contains. In so doing it binds considerable amounts of nitrogen and other nutrients which are then removed from the system when the oysters are harvested. Macroalgae cultures have similar water-purifying effects: they make the water bodies they live in cleaner and more transparent, and autotrophic plant growth on the bed increases, which in turn increases the oxygen content.
Prejudices can be very persistent
Accusations that the increase in aquaculture production leads to overfishing because it raises the demand for fish meal and fish oil are also unfounded. While it is true that the amount of fish and seafood products produced in aquaculture is steadily increasing, this increase is achieved without additional consumption of fishmeal. Global production of fish meal and fish oil has even tended to decline. Between 2000 and 2009, 5.7 million tonnes of fishmeal and 1 million tonnes of fish oil were produced annually, compared to 4.9 million tonnes and 0.9 million tonnes respectively between 2010 and 2018. As an alternative to fish meal and fish oil the feed industry is increasingly using agricultural raw materials and special microalgae products (omega-3-containing algae oil). Conventional salmon feed, for example, now contains on average less than 25% marine ingredients. This development is reflected in the declining FIFO value of aquaculture. FIFO (Fish In: Fish Out) is a calculation of the weight of wild fish in kg needed to produce one kg of farmed fish.
Criticism of the excessive nutrient input of aquacultures into natural waters, on the other hand, is not entirely unjustified. These inputs result in eutrophication effects. However, generalisations are inappropriate because the situation is different at every location and for every form of production and so must be viewed in a differentiated way. Whether ponds, raceway systems, open net enclosures or closed loop systems (RAS): each type of system has its own wastewater characteristics. In some regions of the world there are still companies that simply discharge their nutrient-laden pond water into the environment untreated. However, the number of enterprises that treat their effluent water with mechanical or biological filters or in clarification ponds is increasing. Food residues and fish excreta, which constitute the major share of the waste, are organic nutrients that can be used as fertilizer in agriculture. In enclosed inland waters nutrients often become a problem because they encourage plankton growth and are concentrated in bottom sludge which has to be removed… a task that is both time-consuming and costly. At coastal sites the problems are often less severe because currents and the alternation of ebb and flow ensure rapid distribution across the surface. New technologies such as RAS, Aquaponics or IMTA, which are particularly favoured in industrialised countries, help to reduce nutrient inputs.
Fish diseases and epidemics pose a permanent threat to aquaculture. They not only endanger the fish, mussels, crustaceans and aquatic plants produced but also threaten numerous other species in the immediate vicinity of the farms. Sometimes it is not the diseases alone that are the threat because their control, the selection and use of therapeutic agents, can also be problematic. The public focus here is mainly on antibiotics but other medicines, chemicals (e.g. herbicides to combat vegetation on pond shores) and disinfectants often have undesirable side effects. In the event of a disease within their animal population aquaculture companies often have only limited options for action. They are already obliged to undergo curative treatment for reasons of animal welfare but in EU countries the spectrum of permissible drugs is extremely limited. For some fish species, including salmon, bass and dorade, producers now rely on preventive measures such as vaccination to strengthen the immune system of the farmed species. The vaccination of all salmon smolts before they are released into net enclosures in the sea, for example, has meant that the antibiotics problem in Norway's salmon industry is now practically non-existent. Nevertheless, it is still a hot topic in the media when it comes to salmon from aquaculture.
A much larger problem, for which there is as yet no fully satisfactory solution, is ectoparasites such as sea louse which find optimal living conditions in the dense fish stocks of a salmon farm and spread rapidly. Despite all the attempts to control sea louse (chemical, biological – e.g. with cleaner fish such as young lumpsuckers and wrasses and technical – e.g. with computer-controlled laser cannons), parasites are currently the biggest growth barrier for the salmon industry, although modern computer-generated spatial planning models are now helping to find suitable locations for fish farms.
Animal welfare gaining in importance
An annoying but hardly avoidable problem is escapes, i.e. fish that escape from an aquaculture facility into the natural environment. Annoying, because escapes are always connected with economic losses, and hardly avoidable, because the causes of escapes are mostly accidents, bad weather or human errors, which can never be completely ruled out despite all caution. The biological consequences of escapes for wild fish stocks at the site are controversial. Some aquaculture critics believe that animals from farms are "unfit for life" and can no longer survive on their own in natural surroundings because they have lost many life-supporting instincts. That was why they would die a miserable death once they had left “their farm” behind. Others claim exactly the opposite and declare the farm animals to be strong competitors that are superior to the native fish in many aspects (aggressiveness, reproduction, fighting for feed) and occasionally even invasive. Fears that genetically modified organisms such as AquAdvantage salmon escaping from farms may affect and mate with their wild counterparts are unfounded. On the one hand, the transgenic animals are kept strictly isolated in indoor RAS, on the other hand, they have been rendered sterile, i.e. infertile, by genetic methods.
The ban on organotin compounds such as tributyltin oxide (TBT) which was also used in aquaculture as an effective biocide against biofouling to prevent growth on nets and tank walls has significantly reduced the risk of toxic side effects in many aquatic ecosystems. Among the new antifoulants currently used in practice copper alloys, in particular, have proven their worth because they also have antimicrobial properties and prevent biofouling but are less toxic to other organisms in the environment. However, there is constant progress in this area as well so that even more effective materials might be available in the coming years.
While in the 1990s aquaculture critics mainly focused on fish health and fish transport, now – at the beginning of the 21st century – topics such as stocking density ("mass animal husbandry") and animal-friendly slaughter methods are more in the spotlight. At present, the main focus is on problems of animal welfare. The general definition of the "5 freedoms") in the Brambell Report (1965) which can also be applied to fish is often used to assess fish welfare. While criteria such as species-appropriate feeding, fish health and hygiene and husbandry conditions are relatively easy to define and control this is much more difficult for other characteristics. There is still no accepted scientific method to objectively quantify quality of life, normal behaviour, anxiety, stress and pain in a fish. This makes it quite easy for people who are already hostile to aquaculture to make accusations that, while unprovable, are difficult to refute. If the perception of animal suffering is only based on human experience and on the assumption that fish can have empirically recognizable "emotions" serious debates are difficult because they lack a scientific foundation. Opinion leaders of public criticism are also often ambitious laymen without a professional background which can make discussions with them exhausting and gruelling.
Nevertheless, aquaculture has to rise to this challenge. It has some good and convincing arguments which, unfortunately, are often unknown to the public. Who knows, for example, that aquaculture also contributes to the conservation of endangered species, that modern technologies such as multitrophic production systems, aquaponics, fractionated aquaculture, integrated agricultural/aquaculture and fishery/aquaculture systems or Peri-Urban aquaculture systems are increasingly changing the industry? Global aquaculture is not static but dynamic and it is moving in the direction of ecological sustainability in order to increase its economic stability and improve its social acceptance.