Fish Farming Is Not as Sustainable as We Thought

Fish farming was supposed to be a more sustainable way to meet the global demand for seafood. But as aquaculture gains in popularity, so does its environmental impact.

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Explainer Aquaculture Food

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Fish farming was supposed to be a more sustainable way to meet the global demand for seafood. In recent years, aquaculture has exceeded wild capture in terms of total global production. But do fish farms really reduce pressure on wild populations and help prevent the environmental issues caused by industrial fishing? 

In many ways, the fish farming industry is far from being a perfect solution. While some farming methods are less harmful than others, these intensive operations nonetheless produce a range of negative effects on the environment and the fish themselves. This article will cover the primary types of fish farming as well as some of the species involved and will take a look at some of the negative outcomes arising from the conditions in which farmed fish are kept.

What Is Fish Farming?

Fish farming, also known as pisciculture, is the practice of raising fish for human consumption. Modern industrial fish farming tends to follow intensive agricultural practices, which prioritize maximizing outputs while minimizing inputs by housing large numbers of individual fish within close quarters. The resulting conditions are generally unnatural and can be harmful to both the fish and the surrounding environment. Industrial fish farming closely resembles factory farming of terrestrial animals such as chickens, cows, and pigs. 

Fish farming is a subset of aquaculture, meaning the production of marine life including crustaceans (such as shrimp), mollusks, shellfish, and seaweed. Since 2012, aquaculture has exceeded the total global catch for seafood, thanks in large part to the industrialization of fish farming. 

What Types of Fish Are Farmed?   

There are over 150 species of fish currently farmed around the world. These species include: 

  • Silver carp
  • Common carp
  • Atlantic salmon 
  • Bighead carp
  • Catfish
  • Siberian sturgeon
  • Freshwater bream
  • Pink salmon
  • Whitefish
  • Arctic char
  • Lake trout
  • Grass carp
  • Yellowtail snapper
  • White mullet
  • Bluefin tuna
  • Nile tilapia

According to a 2017 report by the Fish and Agriculture Organization, the top species of fish farmed on a global scale include grass carp, silver carp, Nile tilapia, and common carp.

How Fish Are Bred   

In the wild, fish have particular breeding habits, for example, salmon, who breed after traveling great distances and at particular times of the year. Natural spawning cycles are not accommodated by fish farms; instead, they are manipulated to suit production schedules. Some species of fish do not willingly breed whatsoever in captivity, due to environmental or cultural conditions resulting in stress. For these reasons, the industry tends to induce breeding by a variety of methods. 

A part of breeding inducement in farmed fish is injecting fish with hormones, since, like humans, fish breeding cycles are moderated by these chemicals. An extract of the hormone gonadotropin is made by removing the pituitary gland of a fish—which is located in the brain—and injecting the hormones into another fish. Changing photoperiods or introducing items into the tanks which replicate natural environments can also be used to induce a state of reproductive readiness in fish. 

Once fish have been brought into a reproductive state, the female is “stripped”: her abdomen is squeezed, sending a stream of eggs shooting from her body into a collection basin. In males, sperm can be collected via a similar method of abdominal “massage,” surgically removing testes, or via a catheter that sucks sperm out of the body. Eggs and sperm are then brought together in separate tanks, where eggs are hatched and small fry begin to grow. 

Types of Fish Farms   

While some form of fish farming has been practiced by people for many years, the industrial fish farming industry is relatively recent. Below are a few modern methods for farming fish.

Cage System

A cage system is a common type of fish farming in which cages are set into open water. Cage systems can be rigid, made from wire webbing or stiff plastic mesh, or flexible, made from materials such as nylon. Since fish are kept in unnaturally dense concentrations within the cages, pollutants such as ammonia and nitrates can build up in the water, harming both the farmed fish and the surrounding ecosystem. Cage systems also create ideal conditions for diseases and parasites, often affecting wild fish as well as farmed fish.

Irrigation Ditch Or Pond Systems

Irrigation ditch or pond systems involve keeping fish either within enclosed ponds or sometimes in ditches of agricultural fields. Fish in these systems can either be fed artificially or can exist in a more natural pond setting where plants, algae, and detritus compose the fishes’ diets. The waste products from the fish are used as fertilizer for adjacent agricultural land.

Composite Fish Culture

Composite fish culture involves stocking a pond, lake, or reservoir with the desired fish species, or many species, that coexist together, sometimes alongside native and endemic species. Different feeding areas can be established within the body of water for each species, allowing for maximized yields. Species involved in composite fish culture include rohu, mrigal, and different varieties of carp.

Integrated Recycling Systems

Integrated recycling systems involve bringing fish enclosures, often in the form of large plastic tanks, into a greenhouse that also grows hydroponic plant crops. Water from the fish tanks is circulated among the plants, and the fish waste provides the plants with nutrients. Crops such as basil, parsley, and even marijuana can be grown with integrated recycling systems.

Classic Fry Farming

Classic fry farming, also known as a “flow-through system,” involves incubating fish eggs in hatcheries and raising fish until they are juveniles. Also known as fry, these young capable of feeding themselves. The fry is released into streams to live the full life cycle until they are recaptured as adults. Species used in sport fishing are commonly farmed using the classic fry method. 

Why Is Fish Farming Bad?   

For much of modern history, fish were considered to be closer to inanimate objects than animals; mere streams of protein swimming in the seas, akin to veins of precious metals winding through rock. In more recent years, scientific discoveries proving that fish are sentient, sensitive beings have muddied the ethical waters around what can be considered fair treatment of farmed fish.

The relatively newly-discovered abilities of fish raise questions of whether these animals should be intensively farmed, or at least whether they deserve strengthened welfare standards than are currently offered on farms. Fish can experience pain and have been shown to display aversion behaviors as well as fear under experimental conditions. Certain species have even demonstrated self-awareness by recognizing themselves in mirrors.

Some fish seek out human attention, enjoying belly rubs or cuddling with divers on the seafloor. They can become depressed in captive conditions, with neurochemistry so similar to humans that anti-depression medication designed for people works on even the humblest minnow. When held in crowded, confined spaces, and slaughtered using methods that are deemed to be largely inhumane, the sensitivities of fish can magnify the physical and psychological impacts fish experience. 

Conditions on Fish Factory Farms

Industrial fish farms are generally characterized by high concentrations of fish in small areas. These intensive strategies often result in severely constraining the quality of life for fish, which can manifest as observable pain and stress in farmed conditions. Below are a few ways that fish farms can negatively impact fish. 

Handling and Transportation

Farmed fish get handled throughout their lifespans, including for vaccinations, tagging, and activities associated with breeding. Capturing fish can be extremely stressful for them, and their bodies can endure damage, from injuries to their eyes and fins, or losing scales. Some species are also transported between facilities—another highly unnatural process that can produce stress and cause death.

Lack of Space and Crowded Conditions

In the wild, some species of fish frequently school together in tight groups—however, they tend not to remain in one area for a prolonged period. In farming situations, fish are packed together in relatively small areas for the duration of their lives. The dense concentration means that water can quickly become polluted, thanks to waste generated by the fish themselves and any uneaten fish food.

Onshore facilities can get a better handle on water pollution by installing proper waste filtration systems, but in open-water farming scenarios, the problem is much more difficult to resolve, leading to pollution and degradation of the surrounding ecosystem. Regardless of the farming system, crowding fish into cramped conditions is unnatural and can have negative effects on their welfare. 

Health Impacts

The spread of disease is a major problem with fish farms, particularly in open water systems where illnesses can infect wild populations. Diseases spread quickly on farms given the proximity of bodies, as well as chronic stress, which can depress immune systems and render fish more vulnerable to disease. Salmon anemia, tail rot, fungus, and parasites are among the many forms of disease farmed fish are susceptible to.

Appetite of Farmed Fish 

Rather than removing strain on wild fish populations, fish farms contribute to the overfishing of wild species. Many farmed species of fish are predators—meaning they must be fed other fish to survive. The diets of many farmed fish are therefore composed of wild fish, the harvesting of which causes serious environmental impacts and welfare concerns. Salmon and tuna must consume around five pounds of fish to gain each pound of weight on their bodies. Put another way, it takes 70 wild-caught fish to produce one farm-raised salmon. 


Fish farming comes with a host of problems regarding the environment and the fish themselves. Between pollution of surrounding ecosystems, to the amount of wild fish required to feed farmed individuals, to the welfare concerns of individual fish, the industry has much room for improvement.

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