Fish farming

Fish farming, also called pisciculture, is the growing of fish in tanks or special areas like ponds. It is a type of aquaculture, which means raising water animals such as fish, crustaceans, and molluscs in places we control. The main goal is usually to make food, with common fish like carp, catfish, salmon, and tilapia being farmed.

A fish farm on the coast of Euboea island, in South Euboean Gulf, Greece

As more people need protein from fish, wild fishing has made many fish groups smaller. Fish farming helps by making special places where fish can be fed, kept safe, and caught when we need them. This way, it does not usually hurt wild fish groups. China is the biggest maker of farmed fish, giving more than 60% of the world’s farmed fish.

But farming some fish like salmon can still affect wild fisheries because these fish are often fed food from fish caught in the wild. Fish farming can also cause water pollution and spread sickness to wild fish. There are also worries about how the fish are kept. Besides food, fish farming also gives live fish for aquariums, with most coming from farms in Asia, Europe, Florida, and South America.

Major species

Top 15 cultured fish species by weight, according to FAO statistics for 2013
Species	Environment	Tonnage (millions)	Value (US$ billions)
Grass carp	Freshwater	5.23	6.69
Silver carp	Freshwater	4.59	6.13
Common carp	Freshwater	3.76	5.19
Nile tilapia	Freshwater	3.26	5.39
Bighead carp	Freshwater	2.90	3.72
Catla (Indian carp)	Freshwater	2.76	5.49
Crucian carp	Freshwater	2.45	2.67
Atlantic salmon	Marine	2.07	10.10
Roho labeo	Freshwater	1.57	2.54
Milkfish	Marine	0.94	1.71
Rainbow trout	Freshwater Brackish Marine	0.88	3.80
Wuchang bream	Freshwater	0.71	1.16
Black carp	Freshwater	0.50	1.15
Northern snakehead	Freshwater	0.48	0.59
Amur catfish	Freshwater	0.41	0.55

Categories

Aquaculture uses either local photosynthetic production (extensive) or fish that are fed with external food supply (intensive).

Extensive aquaculture

Intensive aquaculture

See also: Intensive farming

In these systems, fish production per area can be increased as long as there is enough oxygen, fresh water and food. Because of the need for fresh water, a big water purification system must be part of the fish farm. One way to do this is to combine hydroponic horticulture and water treatment, see below. The exception is cages placed in a river or sea, which get enough oxygenated water from the surrounding water. Some environmentalists object to this practice.

Controlling roes manually

The cost of food per amount of fish is higher than in extensive farming, especially because of the high cost of fish feed. It must contain a lot of protein (up to 60%) and a balanced amino acid mix. Fish such as salmon need about 1.1 kg of feed per kg of salmon, while chickens need about 2.5 kg of feed per kg of chicken. Fish do not need energy to stay warm, so their food does not need as many carbohydrates and fats. This can be helped by lower land costs and higher production from more control over inputs.

Aeration of the water is important, as fish need enough oxygen to grow. This is done by bubbling, cascade flow, or adding oxygen to the water. Catfish in genus Clarias can breathe air and can handle more pollutants than trout or salmon, which makes aeration and water purification less needed and makes Clarias species good for intensive fish production. In some Clarias farms, about 10% of the water can be fish biomass.

Very-high-intensity recycle aquaculture systems (RAS, also Recirculating Aquaculture Systems), where all production details are controlled, are used for valuable species. By recycling water, little water is used per amount of production. However, these systems have high costs. Because of the high costs, RAS is only economical for valuable products, such as eggs for breeding, young fish for net pen farming, sturgeon, research animals, and some special markets like live fish.

Raising ornamental coldwater fish (goldfish or koi), although potentially more profitable due to the higher income per amount of fish, has only been done successfully in the 21st century. Today, a few successful intensive koi farms operate in the UK, Germany, and Israel.

In 2016, young Nile tilapia were fed food with dried Schizochytrium instead of fish oil. Compared to a group raised on regular food, they gained more weight and their food was turned into growth better, and their flesh had more healthy omega-3 fatty acids.

Fish farms

Fish farming, also called pisciculture, is a way to raise fish in tanks or special enclosures like ponds. It is a type of aquaculture, which means growing aquatic animals in controlled places. Fish farms can be set up in many ways, each with its own good points.

Fish cages are put in lakes, rivers, or even the ocean. They hold fish until they are big enough to sell. Cages can be made from many materials and are good because they can use many kinds of water. But sometimes cages can break and let fish escape, which can be a problem.

Giant gourami is often raised in cages in central Thailand.

In the Philippines, fish pens are used. These are bigger than cages and use the natural bottom of the water as the floor. They are often used to raise milkfish and can cover large areas of water. Fish pens don’t always need extra food because the fish can eat naturally in the water.

Open net pens are another method where fish are kept in large cages in natural water. The water flows through these cages, but this can sometimes let waste and diseases spread. It’s important to choose a good location for these farms to avoid problems.

Some farms use irrigation ditches or ponds to raise fish. These systems store water and can use plants and algae to feed the fish. Keeping the water clean is very important in these systems.

Fish cages in Lake Victoria, Uganda

One special method is called composite fish culture, used in India. It mixes different kinds of fish in one pond so they don’t compete for food. This method can produce a lot of fish but needs careful management.

Integrated recycling systems combine fish farming with growing plants. The waste from the fish helps feed the plants, and the plants clean the water for the fish. This is a very efficient way to farm fish and grow plants together.

Classic fry farming raises young fish, called fry, in tanks until they are big enough to be released into streams. This method has been used for many years to add fish to rivers for people to catch.

Issues

Fish farming raises concerns about the well-being of the fish. Fish can feel pain and stress in crowded spaces. They may not be able to behave naturally, like building nests.

Another concern is feeding. Some fish need food made from other fish, which comes from catching wild fish. Researchers are working on new feeds made from plants. Keeping too many fish in one place can stress them and make them more likely to get sick.

The number of fish kept in farms can harm the environment. Waste from the fish can pollute the water and affect other sea creatures. Placing farms in certain spots can also cause problems for local marine life.

A North American lake trout fishing farm on Lake Titicaca near Copacabana, Bolivia. Since their introduction in the 1930s, trout have been an invasive species endangering the local fish population.

Mean eutrophying emissions (water pollution)
of different foods per 100g of protein
Food types	Eutrophying emissions (g PO₄^3-eq per 100g protein)
Beef	365.3
Farmed fish	235.1
Farmed crustaceans	227.2
Cheese	98.4
Lamb and mutton	97.1
Pork	76.4
Poultry	48.7
Eggs	21.8
Groundnuts	14.1
Peas	7.5
Tofu	6.2

Mean greenhouse gas emissions for different food types
Food types	Greenhouse gas emissions (g CO2-Ceq per g protein)
Ruminant meat	62
Recirculating aquaculture	30
Trawling Fishery	26
Non-recirculating aquaculture	12
Pork	10
Poultry	10
Dairy	9.1
Non-trawling fishery	8.6
Eggs	6.8
Starchy roots	1.7
Wheat	1.2
Maize	1.2
Legumes	0.25

Indoor fish farming

Indoor fish farming uses special treatments to keep the water clean. This helps reduce problems like fish escaping and pollution.

One challenge is that the water sometimes needs to be changed. But methods like growing plants together with the fish, called aquaponics, can help. These plants clean the water and might reduce the need to change it.

The impact on the environment depends on local water supplies. In places where water is scarce, the water from these farms can help grow crops. Researchers study ways to stack fish tanks to grow more fish in less space, but these methods can be expensive.

Slaughter methods

Main article: Fish welfare at slaughter

There are different ways to prepare fish for food, and some ways are kinder to the fish than others. In the past, some methods used carbon dioxide to make fish sleepy before cutting their gills, but this is now seen as unfair to the fish. Better ways include using electric shocks or quick blows to the head to make the fish sleepy right away.

Some older methods can be hard on fish. For example, leaving fish out of water for a long time or putting them in very cold water can make them feel pain. These methods are being replaced by quicker, kinder ways to make sure fish feel less stress. Using the right electric current or a quick tap to the head can help keep fish sleepy during the process, making it more fair to them.