Ponds are the foundation of global aquaculture
This article was featured in Eurofish Magazine 1 2025.
Aquaculture is often viewed critically, even though it makes an indispensable contribution to the food supply. However, many accusations are unfounded, because the sector is changing very dynamically, and some criticisms have long since become irrelevant. This is particularly true for pond farms around the world. They provide the bulk of production and, as valuable cultural landscapes, also serve to protect the climate, nature, and recreation.
In the public perception, offshore floating net pens, such as those used for salmon farming in Norway, tend to dominate the image of aquaculture. While this is not fundamentally wrong, it is quite unrealistic, because the majority of global aquaculture production is generated by pond farms of all forms. Of the global aquaculture production of 94.4 million tonnes (live weight equivalent, excluding algae and aquatic plants) in 2022, with a total value of USD 295.7 billion, 59.1 million tonnes, or almost two-thirds, were produced in land-based production facilities. Fish account for almost 90% of global inland aquaculture production (89.7%), followed by crustaceans, mainly shrimp (8.7%). Inland aquaculture uses a wide range of methods and technologies, varying significantly in intensity and often combined with other economic activities. Although there are no reliable surveys and clear statements on the share of traditional pond farming, it is generally assumed that man-made ponds are still the most widespread production method.
This is also supported by a Chinese study by Zhihua Wang and other researchers in the International Journal of Applied Earth Observation and Geoinformation (Vol. 115, 2022), which analysed the global distribution of land-based aquaculture ponds based on the 10-m Sentinel-2 time-series images from Google Earth Engine. According to this, 89.12% of the world’s land-based aquaculture is located in Asia. Three-quarters of pond facilities (75.57%) were concentrated in a 30 km wide coastal strip. This result is broadly consistent with the FAO aquaculture statistics and underlines the enormous economic, ecological, and social importance of pond farming for the respective regions and beyond. They make a significant contribution to closing the existing gap between supply and demand for aquaculture food. They create jobs and generate income, thus making an important contribution to the fight against poverty in emerging markets. This effect is further reinforced by the fact that many ponds contain fish species that feed at low trophic level and can be produced extensively without supplementary feeding. For example, in 2022, more than half of global aquaculture production (51.5%) was accounted for by Indian and Asian carp (31.788 million tonnes combined) and catfish species (10.8%; 6.628 million tonnes). The ponds also provide exportable products that are in high demand in other parts of the world. Just think of catfish species such as pangasius or tilapia and other cichlids (10.6%, 6.549 million tonnes). Shrimp and other crustaceans are mainly produced in brackish or seawater ponds.
Ponds have been successfully utilised for centuries
Pond cultures are the most common aquaculture systems in the world. Ponds are usually filled with fresh water, but sometimes with brackish or salt water. They range from small, purely gravity-fed systems to large-scale facilities with sophisticated water management. In the simplest cases, they use irrigated rice fields or dammed natural water bodies. However, the majority of earth ponds are located on dry land and are created by excavating soil or building dams or embankments. The reservoirs constructed in this way are often lined with concrete or tarpaulins to retain river, rain, ground, or well water. Extensively managed ponds are particularly environmentally friendly as a cultural landscape because they provide shelter for numerous animal and plant species. Ponds have been used for food production for thousands of years. The Chinese are believed to have built their first ponds as early as 4,000 years ago. From there, the technology expanded to the Mediterranean through Mesopotamia and rapidly spread across the Roman Empire. The idea was taken up primarily by the monasteries of Central Europe, which then mainly contributed to the domestication of the carp.
However, despite its centuries-old history, pond farming is by no means outdated or outmoded, as it has proven to be highly successful and offers compelling advantages. The construction of a pond is relatively easy and inexpensive, and maintaining it does not require a great deal of effort. This is especially true for extensively managed ponds, which are sometimes even self-sustaining. With their almost closed material and energy cycles, they resemble natural ecosystems, allowing the fish species to feed on what grows there. However, as this natural food source is usually limited, the productivity of such extensive systems is correspondingly low. Low input, low output. This principle works wherever sufficient pond area is available or production is only for regional demand. If there is a higher demand for fish, pond productivity can be increased by intensifying management, which usually involves adding external feed to the pond system. This input enables a correspondingly higher output.
In large, semi-intensive or intensive ponds, fish feed is usually distributed over the surface with specially equipped boats.
Although ponds are relatively easy to maintain compared to other aquaculture systems, pond farmers cannot avoid some cleaning and maintenance tasks. This mainly involves removing the sludge that settles to the bottom over time as a result of dying plankton and aquatic plants, feed residues, and fish excrement. In extensive, near-natural ponds, this waste is almost completely broken down by micro-organisms and returned to the system’s internal nutrient cycle. However, in more intensively managed facilities, these ‘service providers’ find it increasingly difficult to cope with this task, so people have to intervene and remove the sludge. Otherwise, the ponds run the risk of losing depth, becoming overgrown, and silting up. This is the fate of earth ponds that are not regularly maintained. However, the silting of ponds results not only in the loss of reservoirs for fish production but also in the disappearance of biologically important refuges and habitats for many animal and plant species. Ponds make a valuable contribution to practical nature conservation! This is just a warning to those ‘conservationists’ who think that they can preserve these habitats by renouncing the use of pond landscapes.
In coastal villages in India, mud crabs and other crustaceans are often raised in brackish water ponds alongside shrimp.
Production-oriented, yet close to nature
Earthen ponds are, so to speak, man-made natural spaces. However, this also means that, as open systems, they are exposed to numerous external factors that are either entirely or partially beyond the control of the pond farmer. Examples include environmental factors such as temperature and precipitation, as well as oxygen content in the water, or fish losses due to predators ranging from cormorants to otters. Technical aids such as aeration systems or net covers can be used to prevent this, but they are costly and often limited by the size of the ponds. Classic pond cultures generally do not have any special water treatment methods. However, this is often not the case with new and modern pond systems, as the equipment is frequently a requirement for obtaining a permit. Regulatory requirements for pond permits have been significantly tightened, both in Europe and elsewhere in the world. Environmental and water regulations play a much more important role today than just a few years ago. Due to the increased requirements, older existing facilities are also often modernised and retrofitted.
In many areas of Central Europe, carp farming has been a centuries-old tradition. Fishing often takes place during regular festivals.
Technical innovation in pond aquaculture production proves beneficial wherever it contributes to improving production efficiency and reducing environmental impacts. Until a few years ago, environmental aspects hardly played a significant role in Chinese aquaculture. This has now changed dramatically. In many Chinese provinces, canal systems have been constructed in pond landscapes to collect nutrient-rich runoff water and direct it to artificial wetlands for treatment, following the principle of settling ponds. This idea has also been taken up and implemented in other countries, including Vietnam, Colombia, Mexico, Uzbekistan, Bangladesh, and Egypt. In some cases, such integrated systems have even given rise to fish-farming clusters or aqua parks, in which the water is not only shared and purified, but where pond farmers and other businesses involved work together. Typically, the management team then takes over the coordination and monitoring of production processes, which helps to reduce costs, create synergies, and facilitate investment in sustainable infrastructure for a more environmentally-friendly aquaculture in inland areas. Asian pond farms are by no means all primitive old-fashioned systems, but are gradually being developed into state-of-the-art solutions for fish and shrimp farming.
The politically-driven concept of ‘greening’ aquaculture also fits in with the locally coordinated remediation plans, which are slowly evolving into an internationally significant trend. One aspect of this colourful mosaic is the stricter regulation of access to pond farming licenses, which are now granted based on sustainability assessments of water bodies, a shift from previous practices. Potential investors are suddenly realising that environmental and nature conservation concerns are being taken just as seriously as economic interests. This inevitably leads to considerations of how aquaculture activities can be better integrated into local structures in a more environmentally and socially responsible way.
Ponds are oases of nature conservation, serving as habitats for diverse flora and fauna, offering both protection and nourishment.
Modern pond farming methods
In some respects, pond farms have a much better chance of social acceptance in Asia than in Europe. On the one hand, people there have long been familiar with pond farms and appreciate their value for food production. On the other hand, ponds are often closely linked to other activities, particularly in agriculture, so their benefits for food supply are obvious to everyone and need no further explanation.
Integrated Agro-Aquaculture Production Systems (IAA) are proof of this. They combine different aquaculture and agricultural activities, which can take place simultaneously or successively. For example, IAA can include pig, duck, and fish farming, or fish and shrimp farming in rice fields. IAA have existed in East Asia for centuries, but in the 1960s they also spread to Latin America and Africa. Typically, these systems are operated extensively or semi-intensively. In the latter case, the livestock are usually kept directly above the pond in barns with slatted floors, so that the waste ends up in the water and, as fertiliser, promotes the growth of phyto- and zooplankton. This means that more food is available for the fish and the productivity of the ponds increases. While in this case the combination of agriculture and aquaculture is primarily aimed at improving fish growth, the opposite is true in wet rice fields, where the focus is on rice production. Produced fish is a very welcome by-product that improves farmers’ diets by providing high-quality animal protein. There is no need to feed the fish, as they can find enough mosquito larvae in the water of the rice fields, which, in this farming system, function almost like ponds. This also has the welcome side effect of at least somewhat reducing the annoying mosquito population in the area.
Another modern variant of pond farming involves systems where ponds are integrated with agricultural production, utilizing nutrient-rich runoff water from commercially grown crops. This principle is similar to aquaponic systems, which, despite their advantages, have not yet gained widespread adoption in the Western world. One of the main advantages of such coupled production systems is the meaningful use of water resources, including the nutrients dissolved in the water, which would otherwise be lost in pond runoff and contribute to eutrophication of downstream waters. Efficient use of available resources and better environmental protection are the driving forces behind this forward-looking pond farming practice.
More than half of Asia’s inland aquaculture production comes from small and large ponds, from rice fields to professional facilities.
Nature conservation is often more important than fish production
In Asia, Africa, and Latin America, aquaculture is generally highly valued for its contribution to both the regional economy and the food supply for the population. In many places, ponds form part of the cultural landscape, and local fresh food markets sell fish and other pond products. Of course, the industry is not completely free of problems there either, but it is generally accepted and welcomed by the population. In Europe, on the other hand, the situation varies from region to region. While pond farms in the east and south of the continent, or in landlocked areas, generally enjoy a certain degree of acceptance, elsewhere they often face increasing difficulties and sometimes even hostility. The source of many of the problems is rarely the local people who have lived in and benefited from the pond landscape for centuries, but rather self-appointed conservationists and, unfortunately, often the responsible authorities, who view fishing activities only from a purely economic perspective and therefore suspect pond farming of being in opposition to nature conservation.
In their efforts to protect nature and the environment, they are constantly devising new requirements and regulations, which are increasingly perceived as a threat by the pond farmers concerned because they make the core business of the companies more difficult. In addition, there is a feeling of deeply unjust treatment, because pond farmers are already active conservationists who, by maintaining their ponds, make an extremely valuable contribution to the preservation of aquatic and adjacent ecosystems and their biodiversity. Ponds provide much more than healthy, sustainably produced fish products for our nutrition. They retain large amounts of water in the landscape like a sponge and, due to the specific heat capacity of water, act as natural air conditioners that moderate extreme temperatures. The cooling effect of evaporating water is particularly appreciated in hot summers and gives pond landscapes a high recreational value. Unfortunately, the public is often unaware that ponds also serve as natural water purification systems. The solid particles settle and accumulate on the bottom as sludge, which is removed at regular intervals. Dissolved substances, primarily nutrients, enhance the biological productivity of the water, as evidenced by the growth of aquatic plants and reed beds along the banks. They provide food and habitat for a wide range of insects, amphibians, birds, and many other species.
The ‘pond-in-pond’ method is used to create additional, confined habitats in ponds in order to keep and feed fish at higher densities.
On the one hand, politicians and public authorities recognise the contribution that pond farms make to our food supply and to nature conservation. Subsidies are available for pond maintenance, as well as compensation for economic losses incurred by pond farms due to environmental regulations. On the other hand, the same authorities are making the work of pond farmers increasingly difficult by imposing more regulations and reporting obligations on the operations, as well as bureaucratically hindering them. The political will to reduce this demotivating regulatory burden is not even remotely evident at present.
Manfred Klinkhardt