Navigation path

Fisheries

INSEPARABLE - Eat, Buy and Sell Sustainable FishINSEPARABLE - Eat, Buy and Sell Sustainable FishINSEPARABLE - Eat, Buy and Sell Sustainable FishINSEPARABLE - Eat, Buy and Sell Sustainable Fish

Search
    Free text
Subscribe to our e-newsletter
European Market Observatory for Fisheries and Aquaculture Products
Related content
News

Two new reports on the economic performance of the EU aquaculture sector are now available on the website of  the Scientific, Technical and Economic Committee for Fisheries (STECF)

On 15 November 2013, the Directorate-General for Maritime Affairs and Fisheries (DG MARE) organised a workshop on Maritime Spatial Planning (MSP) and fisheries and aquaculture in Vilnius, Lithuania.
A new consultation is on-line. Deadline: 21.02.2014

Aquaculture methods

European aquaculture takes a variety of forms: extensive or intensive, in natural settings or tanks, in fresh water or sea water, in flow-through or recirculation systems, traditional or modern, classic or organic, sheltered or exposed, and so on.

Fact sheet pdf - 725 KB [725 KB] български (bg) čeština (cs) dansk (da) Deutsch (de) eesti keel (et) ελληνικά (el) español (es) français (fr) Gaeilge (ga) italiano (it) latviešu valoda (lv) lietuvių kalba (lt) magyar (hu) Malti (mt) Nederlands (nl) polski (pl) português (pt) română (ro) slovenčina (sk) slovenščina (sl) suomi (fi) svenska (sv)

Extensive aquaculture

The earliest form of aquaculture practiced consisted of trapping wild aquatic animals in lagoons, ponds or small shallow lakes, so that they would be available at all times.
Harvesting of carps in the Czech Republic. © Zbyněk Mejta

This method dates back to the Neolithic age, when man started to act on natural resources, namely around 4000 B.C. in Europe. This minimalist practice no longer exists in Europe because all aquaculture involves at least one technical interaction with the environment or the animal.

In the second stage in its evolution aquaculture no longer relied solely on nature: aquatic environments favourable to the development of fish, molluscs and/or crustaceans were developed. Carp rearing in China is the most sophisticated form of this type of aquaculture, evidence of which dates back to the fifth century B.C. in the famous Treatise written by Fan-Li.

And in Europe? The Romans kept oysters and fattened fish in specially designed tanks. However, it was not until the Middle Ages that pond farming techniques began to develop, particularly in monasteries which needed a non-meat source of food for the many days of fasting imposed by the Christian faith. In southern Europe, fish farming in brackish water also dates back to this time, when lagoons and coastal ponds were first fitted out to retain fish swept in by the tide, including seabass, seabreams and mullets. This practice often alternated on a seasonal basis with salt production.

These forms of aquaculture derived from ancient methods can still be found in Europe. Traditional extensive fish farming is practiced from Lapland to Sicily and from Kerry to Thrace. It consists of maintaining ponds (natural or artificial) and lagoons in such a way that they foster the development of aquatic fauna. Every winter, the ponds and lagoons are cleaned and fertilised to stimulate aquatic vegetation and consequently intensify the presence of micro-organisms, small molluscs and crustaceans, larvae and worms, which form the base of the aquatic food pyramid. This encourages the development of ‘marketable’ animals at a higher yield than that of the natural ecosystem.

In freshwater fish farming, the species produced vary according to regions: river trout, whitefishes, Arctic charr, eel, zander, pike and different species of carp, catfish, sturgeons, crayfishes and frogs. In the past, this activity led to the introduction of many non-indigenous species into the European ecosystem, including rainbow trout, brook trout, carp and different species of frogs and crayfishes. In brackish-water fish farming, depending on their geographical situation lagoons and coastal ponds provide seabass, eels and different species of seabream, mullets, sturgeons, crayfishes and shellfish.





Harvesting of carps in the Czech Republic. © Zbyněk Mejta

This method dates back to the Neolithic age, when man started to act on natural resources, namely around 4000 B.C. in Europe. This minimalist practice no longer exists in Europe because all aquaculture involves at least one technical interaction with the environment or the animal.

In the second stage in its evolution aquaculture no longer relied solely on nature: aquatic environments favourable to the development of fish, molluscs and/or crustaceans were developed. Carp rearing in China is the most sophisticated form of this type of aquaculture, evidence of which dates back to the fifth century B.C. in the famous Treatise written by Fan-Li.

And in Europe? The Romans kept oysters and fattened fish in specially designed tanks. However, it was not until the Middle Ages that pond farming techniques began to develop, particularly in monasteries which needed a non-meat source of food for the many days of fasting imposed by the Christian faith. In southern Europe, fish farming in brackish water also dates back to this time, when lagoons and coastal ponds were first fitted out to retain fish swept in by the tide, including seabass, seabreams and mullets. This practice often alternated on a seasonal basis with salt production.

These forms of aquaculture derived from ancient methods can still be found in Europe. Traditional extensive fish farming is practiced from Lapland to Sicily and from Kerry to Thrace. It consists of maintaining ponds (natural or artificial) and lagoons in such a way that they foster the development of aquatic fauna. Every winter, the ponds and lagoons are cleaned and fertilised to stimulate aquatic vegetation and consequently intensify the presence of micro-organisms, small molluscs and crustaceans, larvae and worms, which form the base of the aquatic food pyramid. This encourages the development of ‘marketable’ animals at a higher yield than that of the natural ecosystem.

In freshwater fish farming, the species produced vary according to regions: river trout, whitefishes, Arctic charr, eel, zander, pike and different species of carp, catfish, sturgeons, crayfishes and frogs. In the past, this activity led to the introduction of many non-indigenous species into the European ecosystem, including rainbow trout, brook trout, carp and different species of frogs and crayfishes. In brackish-water fish farming, depending on their geographical situation lagoons and coastal ponds provide seabass, eels and different species of seabream, mullets, sturgeons, crayfishes and shellfish.





Shellfish farming

Shellfish farming is still an extensive type of aquaculture. It is based primarily on specimens born in the wild and on nutriments provided by the environment, without any type of input.
Mussel farming in Ireland. © Lionel Flageul

Optimal yield can be obtained from nature through sophistication of the process and the techniques used. In Europe, oyster and mussel farming account for 90 % of shellfish farming. Both are very ancient types of farming that date back to Antiquity.

Oyster farming is a traditional activity today in certain EU countries like France (90 % of EU production) and the Netherlands. It is more recent in other countries, especially Ireland. The different types of rearing are based on traditional methods. Two species are cultured in Europe: flat oysters (Ostrea edulis) and Pacific cupped oysters (Crassostrea gigas), the latter being the most widespread. It takes three to four years for oysters to reach commercial size.

Mussel farming also focuses on two species, depending on the geographical area of production: the smaller blue mussels (Mytilus edulis) in northern areas, and the larger Mediterranean mussels (Mytilus galloprovincialis) in southern areas. Rearing methods vary according to species and region.

Other species of shellfish are also cultured in Europe, including carpetshells, clams, scallops and abalones.

The farming of carpetshells (grooved carpetshells or short-necked clams) is more recent. It began in the 1980s, when taking fish by hand or by dredging was discouraged in order to protect resources. Spawning takes place naturally on production sites or is controlled in hatcheries. The spat are reared in cylinders placed in tanks filled with sea water or directly in parks. After three months, the young clams are seeded in intertidal zones (Normandy, Brittany, Cantabria, Galicia) or in lagoons (Poitou-Charentes, Emilia-Romagna, Venetia) and harvested two years later. The bulk of European production is farmed in Italy.





Mussel farming in Ireland. © Lionel Flageul

Optimal yield can be obtained from nature through sophistication of the process and the techniques used. In Europe, oyster and mussel farming account for 90 % of shellfish farming. Both are very ancient types of farming that date back to Antiquity.

Oyster farming is a traditional activity today in certain EU countries like France (90 % of EU production) and the Netherlands. It is more recent in other countries, especially Ireland. The different types of rearing are based on traditional methods. Two species are cultured in Europe: flat oysters (Ostrea edulis) and Pacific cupped oysters (Crassostrea gigas), the latter being the most widespread. It takes three to four years for oysters to reach commercial size.

Mussel farming also focuses on two species, depending on the geographical area of production: the smaller blue mussels (Mytilus edulis) in northern areas, and the larger Mediterranean mussels (Mytilus galloprovincialis) in southern areas. Rearing methods vary according to species and region.

Other species of shellfish are also cultured in Europe, including carpetshells, clams, scallops and abalones.

The farming of carpetshells (grooved carpetshells or short-necked clams) is more recent. It began in the 1980s, when taking fish by hand or by dredging was discouraged in order to protect resources. Spawning takes place naturally on production sites or is controlled in hatcheries. The spat are reared in cylinders placed in tanks filled with sea water or directly in parks. After three months, the young clams are seeded in intertidal zones (Normandy, Brittany, Cantabria, Galicia) or in lagoons (Poitou-Charentes, Emilia-Romagna, Venetia) and harvested two years later. The bulk of European production is farmed in Italy.





Semi-extensive aquaculture

Traditional combined forms of fish farming in ponds and lagoons increasingly evolved into more managed production modes described as semi-extensive aquaculture.

Floating cages in Cyprus. © Lionel Flageul

Traditional combined forms of fish farming in ponds and lagoons increasingly evolved into more managed production modes described as semi-extensive aquaculture. Producers were no longer satisfied with enhancing the natural development of the pond or lagoon. They began to assist nature by introducing fry from hatcheries into the sites and providing supplemental feed. The best example is the rearing of carp in ponds, which is very widespread in the central European countries. Aquaculture in brackish water in southern Europe also turned more to hatcheries and commercial feed to compensate for the decline in natural recruitment. In Italian valliculture in the Po and Adige deltas, lagoons are seeded with seabass and seabream fry to make up for the increased scarcity of these species in the wild and to compensate for the disappearance of eels. In Spanish esteros and in Portugal, this practice has led to testing with new species, including turbot, common sole and Senegalese sole.

To be complete, this overview should also mention conservation in tanks, either floating at sea or in permanent structures on land. This practice is related to fisheries. It is used to conserve and fatten caught animals for subsequent marketing. This type of conservation primarily concerns animals whose taste quality suffers when they undergo classic conservation processes such as sterilisation or freezing. The most common example is that of large crustaceans, like European lobster, spiny lobsters and edible crabs. The fishing season for these shellfish is in spring, but they are traditionally eaten at end-of-year festivities, in winter. Another more controversial example is the fattening of bluefin tuna in floating cages, which appeared in the 1990s in the Mediterranean. In this case, the aim is maintain specimens caught during the spring fishing season and to export them in winter at a higher price.





Floating cages in Cyprus. © Lionel Flageul

Traditional combined forms of fish farming in ponds and lagoons increasingly evolved into more managed production modes described as semi-extensive aquaculture. Producers were no longer satisfied with enhancing the natural development of the pond or lagoon. They began to assist nature by introducing fry from hatcheries into the sites and providing supplemental feed. The best example is the rearing of carp in ponds, which is very widespread in the central European countries. Aquaculture in brackish water in southern Europe also turned more to hatcheries and commercial feed to compensate for the decline in natural recruitment. In Italian valliculture in the Po and Adige deltas, lagoons are seeded with seabass and seabream fry to make up for the increased scarcity of these species in the wild and to compensate for the disappearance of eels. In Spanish esteros and in Portugal, this practice has led to testing with new species, including turbot, common sole and Senegalese sole.

To be complete, this overview should also mention conservation in tanks, either floating at sea or in permanent structures on land. This practice is related to fisheries. It is used to conserve and fatten caught animals for subsequent marketing. This type of conservation primarily concerns animals whose taste quality suffers when they undergo classic conservation processes such as sterilisation or freezing. The most common example is that of large crustaceans, like European lobster, spiny lobsters and edible crabs. The fishing season for these shellfish is in spring, but they are traditionally eaten at end-of-year festivities, in winter. Another more controversial example is the fattening of bluefin tuna in floating cages, which appeared in the 1990s in the Mediterranean. In this case, the aim is maintain specimens caught during the spring fishing season and to export them in winter at a higher price.





Rearing for restocking purposes

Starting in the 17th century, freshwater fish stocks began to decline in certain places, probably due to increases in the human population. The authorities started to explore the idea of restocking rivers with fry hatched in captivity.

Rearing in hatcheries. © Lionel Flageul

In nature, fish release a huge number of eggs and only a few individuals reach adulthood after surviving predators, disease, the lack of food, pollution, thermal shock and other dangers. Hatcheries not only provide fertilised eggs, they also to control all parameters so that a maximum number of individuals can reach the juvenile stage, when they can be released into the natural environment with a good chance of survival.

In 1741, Stephan Ludwig Jacobi, a German multidisciplinary scientist, built the first trout hatchery in Westphalia. It took another century for his discovery to be implemented on a large scale to restock bodies of water depleted by the first effects of the Industrial Revolution in Europe, the United States and Japan.

Scientific research then went on to include charrs, whitefishes, Atlantic Salmon and also the rainbow trout in the United States, which was introduced into Europe in 1874 thanks to its excellent performances. This progress is nonetheless limited to salmonids, which are relatively easy to reproduce in captivity.

It was not until 1934 that hormonal induction was discovered in Brazil and tested on local fish. This technique consists of injecting certain hormones into fish to obtain at will the release of gametes, from both females and males. This discovery offered new prospects to hatcheries and made it possible to consider farming new species that until then had been rendered sterile by the stress of captivity. In 1935 in the then USSR, Soviet researchers obtained fry from several species of sturgeons and even developed hybrid stocks.
The restocking of the ecosystem is still widely practiced today in both fresh water and the marine environment. Hatcheries that operate in this framework are generally financed by public scientific research programmes and focus mainly on indigenous species. For instance, as a result of improved water quality and infrastructure works aimed at restoring freedom of movement for migratory species, several European hatcheries are working on the restocking of rivers with salmon and sturgeons.

Such public-interest hatcheries can also be involved in ‘sea ranching’ projects. Launched in the 19th century, this practice consists of reinforcing a natural stock with young fish from hatcheries to maintain a fishing activity that depends on the stock, e.g. Baltic Sea salmon or common sole in the North Sea. The discoveries made by these scientific hatcheries are often put to use in commercial aquaculture.





Rearing in hatcheries. © Lionel Flageul

In nature, fish release a huge number of eggs and only a few individuals reach adulthood after surviving predators, disease, the lack of food, pollution, thermal shock and other dangers. Hatcheries not only provide fertilised eggs, they also to control all parameters so that a maximum number of individuals can reach the juvenile stage, when they can be released into the natural environment with a good chance of survival.

In 1741, Stephan Ludwig Jacobi, a German multidisciplinary scientist, built the first trout hatchery in Westphalia. It took another century for his discovery to be implemented on a large scale to restock bodies of water depleted by the first effects of the Industrial Revolution in Europe, the United States and Japan.

Scientific research then went on to include charrs, whitefishes, Atlantic Salmon and also the rainbow trout in the United States, which was introduced into Europe in 1874 thanks to its excellent performances. This progress is nonetheless limited to salmonids, which are relatively easy to reproduce in captivity.

It was not until 1934 that hormonal induction was discovered in Brazil and tested on local fish. This technique consists of injecting certain hormones into fish to obtain at will the release of gametes, from both females and males. This discovery offered new prospects to hatcheries and made it possible to consider farming new species that until then had been rendered sterile by the stress of captivity. In 1935 in the then USSR, Soviet researchers obtained fry from several species of sturgeons and even developed hybrid stocks.
The restocking of the ecosystem is still widely practiced today in both fresh water and the marine environment. Hatcheries that operate in this framework are generally financed by public scientific research programmes and focus mainly on indigenous species. For instance, as a result of improved water quality and infrastructure works aimed at restoring freedom of movement for migratory species, several European hatcheries are working on the restocking of rivers with salmon and sturgeons.

Such public-interest hatcheries can also be involved in ‘sea ranching’ projects. Launched in the 19th century, this practice consists of reinforcing a natural stock with young fish from hatcheries to maintain a fishing activity that depends on the stock, e.g. Baltic Sea salmon or common sole in the North Sea. The discoveries made by these scientific hatcheries are often put to use in commercial aquaculture.





Intensive freshwater fish farming

An intensive freshwater fish farming site is generally composed of several rectangular concrete tanks of different sizes and depths suited to the different stages of growth of the fish. A race taps river water upstream and returns it to the river downstream after it has flowed through all the tanks. This is what is known as a flow-through system.

Trout farming in Ireland. © Lionel Flageul

From the end of the 19th century, rainbow trout served as a guinea-pig for progress in European fish farming. This American species proved to be better adapted to aquaculture than its European cousin: it is hardier, grows faster and can put up with higher rearing densities. Until the mid-20th century, however, aquaculture performances were limited because of unsuitable feed, composed mainly of non-processed fish waste, and excessive vulnerability to the epizootic diseases that plagued fish reared in high densities in sites open to attacks from external sources. Progress in the 20th century brought about a change.

It was discovered that every species not only needs a specific type of feed, but also that it must be different at every stage of its development. Many larvae can only survive on live plankton, which have to be produced in captivity, sheltered from microbes and viruses. For young and adult fish, the production of dry pellets represented major progress, but then scientists had to determine the right dose of animal and vegetable proteins, fats, mineral salts, vitamins and other additives, as well as the shape of the pellets and feeding frequency… On health, discoveries in the field of medicines, vaccination and prevention made it possible to combat diseases.

In the 1960s this progress led to the commercial development of intensive rainbow trout farming, first in Denmark and then throughout Europe. Today, European fish farming has diversified considerably, in terms of both product quality and species. Alongside rainbow trout, which still dominates, other freshwater fish are reared intensively: river trout, brook trout, Arctic charr, whitefishes, tilapia, zander, Siberian sturgeon, etc.

Today, however, flow-through systems are being supplanted by water recirculation systems. In such installations, the water remains in a closed circuit and is recycled so it can be ‘recirculated’ in the tanks using a piping system. One of the advantages of this system is its isolation from the external environment, which means that all the parameters of the water can be controlled: temperature, acidity, salinity, disinfection, etc. It also allows for organic waste to be treated before being disposed of in nature. Its drawbacks, apart from the cost of the investment, include its energy consumption and dependence on a complex technology.

Recirculation is not a recent innovation. It is an old practice in aquariums and hatcheries. It was first used in fattening units in the 1980s and today has met with a fair amount of success, particularly in countries with extreme climates, because it allows the water temperature to be controlled, winter and summer alike. In fresh water, this system is mainly used for rainbow trout, catfish and eel, but it is suited to all species, including marine species like turbot.





Trout farming in Ireland. © Lionel Flageul

From the end of the 19th century, rainbow trout served as a guinea-pig for progress in European fish farming. This American species proved to be better adapted to aquaculture than its European cousin: it is hardier, grows faster and can put up with higher rearing densities. Until the mid-20th century, however, aquaculture performances were limited because of unsuitable feed, composed mainly of non-processed fish waste, and excessive vulnerability to the epizootic diseases that plagued fish reared in high densities in sites open to attacks from external sources. Progress in the 20th century brought about a change.

It was discovered that every species not only needs a specific type of feed, but also that it must be different at every stage of its development. Many larvae can only survive on live plankton, which have to be produced in captivity, sheltered from microbes and viruses. For young and adult fish, the production of dry pellets represented major progress, but then scientists had to determine the right dose of animal and vegetable proteins, fats, mineral salts, vitamins and other additives, as well as the shape of the pellets and feeding frequency… On health, discoveries in the field of medicines, vaccination and prevention made it possible to combat diseases.

In the 1960s this progress led to the commercial development of intensive rainbow trout farming, first in Denmark and then throughout Europe. Today, European fish farming has diversified considerably, in terms of both product quality and species. Alongside rainbow trout, which still dominates, other freshwater fish are reared intensively: river trout, brook trout, Arctic charr, whitefishes, tilapia, zander, Siberian sturgeon, etc.

Today, however, flow-through systems are being supplanted by water recirculation systems. In such installations, the water remains in a closed circuit and is recycled so it can be ‘recirculated’ in the tanks using a piping system. One of the advantages of this system is its isolation from the external environment, which means that all the parameters of the water can be controlled: temperature, acidity, salinity, disinfection, etc. It also allows for organic waste to be treated before being disposed of in nature. Its drawbacks, apart from the cost of the investment, include its energy consumption and dependence on a complex technology.

Recirculation is not a recent innovation. It is an old practice in aquariums and hatcheries. It was first used in fattening units in the 1980s and today has met with a fair amount of success, particularly in countries with extreme climates, because it allows the water temperature to be controlled, winter and summer alike. In fresh water, this system is mainly used for rainbow trout, catfish and eel, but it is suited to all species, including marine species like turbot.





Intensive sea farming

In the 1960s, a major innovation in fish farming was developed in Japan: the floating cage.

Harvesting of salmons in Ireland. © Lionel Flageul

Fish are held captive in a large pocket-shaped net anchored to the bottom and maintained on the surface by a rectangular or circular floating framework, originally made of bamboo but soon replaced by plastic. The Japanese used the device to fatten amberjacks and seabream. The idea was exported to Europe, where floating cages were originally used to farm rainbow trout in the sheltered waters of the Norwegian fjords.

In the late 1960s, the cages arrived just at the right time for testing with a new species: Atlantic salmon. The hatchery stage had been perfected years earlier and was producing ample smolts, young fish that have acquired the ability to live in the marine environment. Little time was wasted before taking the step of fattening the young fish at sea in floating cages until they reach adulthood. European salmon farming subsequently became a success story of the 1970s and 1980s. Salmon, due to its scarcity in the wild, had become a luxury product. Its new availability at a reasonable price proved to be an unprecedented commercial success that turned sea farming into an up-and-coming sector in Europe. Farms cropped up in fjords and bays in the North Sea and west of the British Iles, especially in Norway and Scotland.

This Nordic success gained followers. The Mediterranean countries studied and developed the rearing of seabass and gilthead seabream. During the 1990s, farming of these species spread throughout the Mediterranean and the Canary Islands. Salmon, seabass and seabream remain the flagship products of European sea farming, with a diversification of quality that responds to different market segments. Other species are slowly starting to be reared in cages, e.g. croakers in the South and cod in the North.

The 1990s and 2000s saw the development of another form of intensive seafarming, this time of flatfishes. Floating cages are not suited to these fish, which need to rest on a sandy bottom. Tanks on land supplied with sea water were therefore introduced, leading to the development of turbot farming in Galicia. Progress in recirculation technology now offers new prospects for land-based mariculture. Its use is being investigated for other species, such as common sole, reared in flat tubs placed one on top of the other. What is more, the possibility of controlling the water parameters, particularly its temperature, frees the activity from climate constraints. The farming of turbot, seabass and seabream is thus expanding to the north of Europe.

The start of the 21st century nevertheless brings a sizeable new challenge for aquaculture. European coastal zones are saturated with activity and have no land to offer for the expansion of aquaculture. Sea farming is obliged to move further away from the coast. It can move inland, thanks to recirculation systems, but the cost of artificial reconstitution of sea water is a disadvantage. It can also move offshore, far from sheltered coastal areas. Offshore mariculture is the new field of research in European aquaculture. The technological challenges are tremendous, though. The Mediterranean is one of the world’s deepest seas and the Northeast Atlantic is one of the planet’s windiest and stormiest zones. New systems, such as submersible cages, have to be developed to keep fish enclosed but solutions are also needed for their feeding and remote monitoring...





Harvesting of salmons in Ireland. © Lionel Flageul

Fish are held captive in a large pocket-shaped net anchored to the bottom and maintained on the surface by a rectangular or circular floating framework, originally made of bamboo but soon replaced by plastic. The Japanese used the device to fatten amberjacks and seabream. The idea was exported to Europe, where floating cages were originally used to farm rainbow trout in the sheltered waters of the Norwegian fjords.

In the late 1960s, the cages arrived just at the right time for testing with a new species: Atlantic salmon. The hatchery stage had been perfected years earlier and was producing ample smolts, young fish that have acquired the ability to live in the marine environment. Little time was wasted before taking the step of fattening the young fish at sea in floating cages until they reach adulthood. European salmon farming subsequently became a success story of the 1970s and 1980s. Salmon, due to its scarcity in the wild, had become a luxury product. Its new availability at a reasonable price proved to be an unprecedented commercial success that turned sea farming into an up-and-coming sector in Europe. Farms cropped up in fjords and bays in the North Sea and west of the British Iles, especially in Norway and Scotland.

This Nordic success gained followers. The Mediterranean countries studied and developed the rearing of seabass and gilthead seabream. During the 1990s, farming of these species spread throughout the Mediterranean and the Canary Islands. Salmon, seabass and seabream remain the flagship products of European sea farming, with a diversification of quality that responds to different market segments. Other species are slowly starting to be reared in cages, e.g. croakers in the South and cod in the North.

The 1990s and 2000s saw the development of another form of intensive seafarming, this time of flatfishes. Floating cages are not suited to these fish, which need to rest on a sandy bottom. Tanks on land supplied with sea water were therefore introduced, leading to the development of turbot farming in Galicia. Progress in recirculation technology now offers new prospects for land-based mariculture. Its use is being investigated for other species, such as common sole, reared in flat tubs placed one on top of the other. What is more, the possibility of controlling the water parameters, particularly its temperature, frees the activity from climate constraints. The farming of turbot, seabass and seabream is thus expanding to the north of Europe.

The start of the 21st century nevertheless brings a sizeable new challenge for aquaculture. European coastal zones are saturated with activity and have no land to offer for the expansion of aquaculture. Sea farming is obliged to move further away from the coast. It can move inland, thanks to recirculation systems, but the cost of artificial reconstitution of sea water is a disadvantage. It can also move offshore, far from sheltered coastal areas. Offshore mariculture is the new field of research in European aquaculture. The technological challenges are tremendous, though. The Mediterranean is one of the world’s deepest seas and the Northeast Atlantic is one of the planet’s windiest and stormiest zones. New systems, such as submersible cages, have to be developed to keep fish enclosed but solutions are also needed for their feeding and remote monitoring...