Aquaculture

Aquaculture, also called aquafarming, is the controlled farming of aquatic organisms such as fish, crustaceans, mollusks, algae, and other valuable aquatic plants like lotus. Unlike commercial fishing, which catches wild fish, aquaculture grows these organisms in freshwater, brackish water, or saltwater under controlled or semi-natural conditions. This includes practices like mariculture in seawater and pisciculture for producing fish products as food.

Aquaculture can happen in many places: in artificial facilities on land such as fish tanks, ponds, or aquaponics; in sheltered nearshore areas of a body of water; or in enclosed sections of open water using cages or bags. According to the Food and Agriculture Organization, aquaculture involves activities like regular stocking, feeding, and protection to increase production.

In 2019, global aquaculture produced over 120 million tonnes worth about US$274 billion, and by 2022, this grew to 130.9 million tonnes valued at USD 312.8 billion. Aquaculture helps provide food, support healthier habitats, and restore endangered species. However, it also faces challenges, such as needing large amounts of wild fish to feed certain farmed fish and potential environmental impacts like nutrient pollution.

Overview

The growing need for food and the difficulty of catching enough wild fish has led people to farm aquatic animals and plants, a practice called aquaculture. This method helps meet the demand for seafood without relying solely on wild catches.

Scientists have domesticated many marine species for farming, which involves less risk to humans compared to farming land animals. New methods, like using certain fish to keep others healthy, are being developed to make aquaculture better for the environment. However, challenges remain, such as finding sustainable food for farmed fish and creating safe materials to protect equipment.

Species groups

Main species groups

Minor species groups

Aquatic plants

See also: Algaculture and Seaweed farming

Microalgae, also called phytoplankton, microphytes, or planktonic algae, make up most of the algae that are grown. Seaweed is also used for many jobs, but it is hard to grow on a big scale because of its size and special needs, so most seaweed is taken from the wild.

In 2016, about 96.5 percent of all water plants came from farming. The amount of farmed water plants grew from 13.5 million tonnes in 1995 to more than 30 million tonnes in 2016.

Seaweed farming

Fish

Main article: Fish farming

Farming fish is the most common type of aquaculture. It means raising fish in tanks, fish ponds, or ocean spaces, usually to eat. Some places let young fish go back into the wild to catch more fish later or to add to the number of fish in nature. The most common fish to farm are carp, salmon, tilapia, and catfish.

In the Mediterranean, young bluefin tuna are caught and moved slowly to shore. They are kept in special nets in the water to grow bigger. In 2009, scientists in Australia made southern bluefin tuna have babies in tanks on land. These tuna are also caught from the wild and kept in cages in the sea to grow fatter in places like Spencer Gulf, South Australia.

The same idea is used for farming salmon. Young salmon are taken from places where they are born and helped to grow up. One way is to keep them in nets in the water with good flow and give them special food. This helps them grow all year and gives more fish when it is the right time to catch them. Another way is to keep them for a short time and then let them go into the sea to grow more, and catch them later when they are bigger.

Crustaceans

See also: Shrimp farming and Freshwater prawn farming

Farming shrimp started in the 1970s and grew very fast. By 2003, the world made more than 1.6 million tonnes, worth about US$9 billion. Most farmed shrimp come from Asia, especially China and Thailand. The rest comes mainly from Latin America, with Brazil as the biggest maker. Thailand is the biggest seller.

Shrimp farming has changed from small farms in Southeast Asia to a big industry around the world. New technology lets farmers put more shrimp in a small space, and baby shrimp are sent all over the world. Almost all farmed shrimp are a special kind called penaeids, and two types, the Pacific white shrimp and the giant tiger prawn, make up about 80% of all farmed shrimp. These big farms can get sick very easily, which has hurt shrimp in many places. Because of problems for nature, diseases, and worries from groups and countries that buy the shrimp, the industry changed in the late 1990s to use better ways to farm. In 1999, governments, companies, and groups that care about nature started a plan to make farming better through the Seafood Watch program.

Freshwater prawn farming has many of the same issues as shrimp farming in the sea. The main kind of freshwater prawn has its own special life cycle that makes farming it harder.

In 2007, the world made about 460,000 tonnes of freshwater prawns, worth more than 1.86 billion dollars. China also made about 370,000 tonnes of Chinese river crab.

There is also farming of crayfish in fresh water, mostly in the US, Australia, and Europe.

Molluscs

See also: Oyster farming and Geoduck aquaculture

Farmed shellfish include different kinds of oyster, mussel, and clam species. These animals eat from the water and don’t need special food, so farming them is often seen as good or even helpful.

Depending on the kind and where they are, these shellfish are grown on beaches, on lines in the water, or hanging from floats and collected by hand or with special tools. In May 2017, a group in Belgium put the first of two trial mussel farms on a wind farm in the North Sea.

Farming abalone started in the late 1950s and early 1960s in Japan and China. Since the mid-1990s, this industry has grown a lot. Because people took too many abalone from the wild, most abalone meat now comes from farms. Farms that take care of the environment can get certificates from Seafood Watch and other groups, including the World Wildlife Fund (WWF). WWF started the "Aquaculture Dialogues" in 2004 to make rules for farming seafood in a responsible way. In 2009, WWF started the Aquaculture Stewardship Council with another group to manage these rules around the world.

After testing in 2012, a commercial "sea ranch" was made in Flinders Bay, Western Australia, to grow abalone. The ranch uses an artificial reef made of 5000 separate concrete parts called abitats. Each abitat can hold 400 abalone. The reef is seeded with young abalone from a place on land. The abalone eat seaweed that grows naturally on the habitats, and the bay also helps other fish grow.

Other groups

Other groups include water reptiles, animals that live in water but are not fish, and many other sea animals, such as echinoderms and jellyfish. They are shown separately because they do not make up enough to show clearly on the main chart.^{[citation needed]}

Commonly farmed echinoderms are sea cucumbers and sea urchins. In China, sea cucumbers are farmed in very big artificial ponds.

Global fish production

Global fish production reached about 182 million tonnes in 2021, with nearly equal amounts from wild-caught fish and aquaculture. Aquaculture, which involves farming aquatic animals and plants in controlled environments, has grown quickly over the past few decades. It now provides about half of all fish used for food worldwide.

Aquaculture is especially important in China, where it has been a major part of the economy for many years. Other countries, like Chile, have also become big players in farming certain types of fish, such as salmon. The industry supports many jobs, with millions of people working in fishing and aquaculture, especially in Asia and Africa.

Over-reporting by China

China reports very high amounts of aquaculture production, more than the rest of the world combined. Some scientists have questioned whether these numbers are completely accurate. They suggested that in the past, China may have reported higher numbers to meet government goals. However, China defended its reports, saying they were correct. The United Nations' food agency noted that there were concerns about the reliability of some of China's data during that time.

Aquacultural methods

Main article: Mariculture

Main article: Integrated multi-trophic aquaculture

Mariculture is the farming of sea creatures in seawater. This can happen near the coast, far out in the ocean, or even on land. Farmers grow things like seaweed, shrimp, lobster, oysters, and fish such as salmon. Some animals, like salmon, are kept in special nets and fed by people, while others, like oysters, eat naturally from the water around them.

Integrated multi-trophic aquaculture is a way to farm where the waste from one animal helps feed another. For example, waste from fish can be used to grow plants or feed shellfish. This helps keep the water clean, supports many types of animals, and makes farming more stable and friendly to nature. Different kinds of animals work together, each helping the others grow better.

Netting materials

Different materials are used to make nets for farming fish and other sea creatures. These include nylon, polyester, polypropylene, polyethylene, plastic-coated wire, rubber, special rope products, galvanized steel, and copper. These materials are chosen because they are strong, last a long time, and don’t cost too much.

Recently, copper alloys have become popular for making these nets. They help keep the water clean by stopping tiny living things like bacteria, viruses, fungi, algae, and other microbes from growing on the nets. This makes it easier and cheaper to keep the fish healthy and happy.

Main article: Copper alloys in aquaculture

Technology

People are using special uncrewed boats, like ROVs and AUVs, to help with farming fish and other sea creatures. These boats can check on nets, watch the environment, and make things safer and faster. Before, people had to dive underwater to check the nets, but now these boats do it more quickly.

New computer programs can now spot and sort different kinds of fish underwater. Also, a method called biofloc technology helps keep the water clean while giving food to the animals being raised.

Issues

See also: Issues with salmon aquaculture

When not carefully planned, farming fish in lakes or rivers can harm the environment more than catching wild fish, though it creates less waste overall. Problems can include managing waste, effects of medicines used to keep fish healthy, and competition between farm fish and wild fish. There is also a risk of introducing new plants or animals that can cause problems.

Fish waste is natural and contains nutrients that help all parts of water ecosystems. However, farming fish in the ocean often creates too much waste, which settles on the sea floor and can damage animals that live there. The waste can also lower oxygen levels in the water, making it harder for wild fish to survive. One way to help is by building artificial reefs that give more space for sea life without adding extra food.

Impacts on wild fish

Some farm fish are fed wild fish to help them grow. While this is only a small part of all fish farming, it uses up many wild fish. For example, to grow one kilogram of farmed salmon, several kilograms of wild fish are needed as food. This can put pressure on wild fish populations that depend on the same food.

Another concern is that farm fish might escape and mix with wild fish, which can change the genes of wild populations.

Animal welfare

See also: Pain in fish and Pain in invertebrates

When farming animals, it is important to treat them well. This means making sure they are healthy, comfortable, and not scared or stressed. Some people wonder if fish and other sea animals can feel pain. Research shows that fish can sense harmful things, so it is important to care for them properly.

Coastal ecosystems

Farming fish near coasts can harm important areas like mangroves, which are forests that protect coastlines. Some of these areas have been lost to make space for fish farms, which can cause long-term damage.

Freshwater ecosystems

Experiments show that farming fish in lakes can change the water and harm the plants and animals that live there.

Genetic modification

Some fish, like a special type of salmon, have been changed through science to grow faster. However, these fish have not been approved for widespread use because of concerns.

Fish diseases, parasites and vaccines

One big challenge in fish farming is keeping fish healthy. Diseases can spread quickly in crowded farms. Vaccines are an important way to protect fish from diseases without using medicines that can harm the environment.

Salinization/acidification of soils

When fish farms are left unused, the land can become too salty or acidic, making it hard to use for farming again.

Plastic pollution

Fish farming can also create plastic waste, such as pieces from nets and floats, which can end up in the ocean and harm sea life.

Ecological benefits

See also: Nitrate vulnerable zone

Some types of aquaculture can help the environment. For example, farming shellfish like oysters can improve water quality because they clean the water by eating tiny plants and removing nutrients. This helps keep the water clear and supports more plants and animals.

Aquaculture can also create homes for small sea creatures, helping them stay safe and grow. This can support more fish and other sea life. Farming seaweed can also help reduce carbon in the air and improve the health of ocean areas.

Prospects

Global wild fisheries are decreasing, and important habitats like estuaries are in poor condition. Farming certain fish, such as salmon, can also cause problems because these fish need to eat other fish to grow, which takes away from wild fish populations and can harm both wild salmon and the smaller fish used for food.

However, not all aquaculture is harmful. Some types, like growing seaweed or farming oysters, clams, mussels, and scallops, can actually help the environment. These animals clean the water by eating pollutants and nutrients, which improves water quality. Seaweed also takes nutrients like nitrogen and phosphorus directly from the water.

New farming methods aim to reduce harm to the environment. These include ways to lower stress on fish, letting farms rest between growing periods, and using natural ways to control pests. Vaccines are also being used more to prevent diseases without needing as many antibiotics.

Some farms recycle their water by filtering out waste and then using the clean water again. This saves water and the waste can be used to make compost or even treated for use on land. Scientists have found ways to farm saltwater fish in special tanks with less salty water, which could help protect wild fish and reduce costs.

A few countries, such as China, Israel, and the United States, use natural heat from the earth to keep water warm for fish farms year-round. For example, in California, fish farms use this warm water to grow tilapia, bass, and catfish more quickly.

National laws, regulations, and management

Laws about growing fish and other water animals change a lot from country to country and are sometimes hard to follow.

In the United States, rules for growing fish on land or close to the shore are made at the national and state levels. There are no national rules for growing fish far out in the ocean. In 2011, groups like the Department of Commerce worked together to make new rules to help meet the need for healthy food, create jobs, and protect nature. Big fish farms that release water need special permission, and very big farms must follow special rules about what they can release into the water.

By country

Aquaculture is practiced in many countries around the world. Each country has its own ways of farming aquatic animals and plants, using both fresh water and salt water. This helps provide food and jobs in many places.

History

The Gunditjmara, a group of Aboriginal Australians in south-western Victoria, Australia, may have raised short-finned eels as early as about 4,580 BCE. They created channels and dams near Lake Condah and used traps to catch and store eels for food all year.

Oral stories from China talk about farming carp around 2000–2100 BCE, with the oldest written records from around 475 BCE. Early farmers used natural materials to help their fish grow. Ancient Egyptians may have farmed fish from Lake Bardawil around 1,500 BCE, trading them with nearby areas.

In Korea, people have farmed a type of seaweed called "gim" for a very long time, using bamboo sticks and later nets. Japanese people grew seaweed by placing bamboo poles and oyster shells in the water. Romans kept fish in ponds and farmed oysters along coastlines before 100 CE.

In medieval Europe, monasteries continued these practices because fish was an important food source, especially on days when meat was not allowed. As transportation improved in the 1800s, fresh fish became easier to get, making aquaculture less common in some places. Fishponds in the Trebon Basin in the Czech Republic remain important today.

People in Samoa and Hawaii also developed their own ways of farming sea creatures. In the 1700s, a German scientist named Stephan Ludwig Jacobi began experiments with breeding trout and salmon in labs. By the late 1800s, fish hatcheries had been set up in Canada, the United States, and Newfoundland. These facilities helped people raise fish more efficiently.