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Are fish sentient?

Fish are sentient animals capable of feeling pain, stress and fear, as well as experiencing positive emotions, social bonds, and advanced intelligence. They are intelligent, sensitive creatures and like many other animals, they explore, socialise, hunt and play. Some species care for their young and use tools as we humans do.

Today, huge numbers of fish are intensively reared on farms where they are forced to live in conditions that fail to meet their basic welfare needs and many are dying prematurely every year.

What is aquaculture?

What is aquaculture?

What is aquaculture?

Aquaculture is the controlled process of farming seafood (fish, crustaceans, molluscs, seaweed), especially for human consumption. As the demand for seafood has increased, technology has made it possible to rear common fish species in sea cages in coastal marine waters and in the open ocean.

It is the world’s fastest-growing food production sector which is increasingly dwarfing the traditional fishing industry. It now produces more than $263 billion worth of goods annually, and over half of the seafood we consume today is farmed, which may come as a surprise to many consumers.

Aquaculture in numbers

In 2019, 56% (FAOSTAT 2021) of all seafood consumed worldwide was produced in aquaculture facilities. This is expected to grow even further (up to 32%) as wild-caught fishing plateaus, due to overfishing and biological constraints; the fish cannot reproduce fast enough for their populations to recover, and climate change and human interventions are affecting their environments making it more difficult for them to reproduce.

In aquaculture, fish production is generally measured in tonnes rather than individual fish so estimating the number of fish produced in these facilities can be difficult to calculate due to the diversity of species and harvest weights. However, here are some estimates for three of the key farmed fish species (2018 figures):

  • Atlantic Salmon - up to 674 million fish produced
  • Sea Bass - up to 955 million fish
  • Sea Bream – up to 1,035 million fish

Approximately 109 billion fish are farmed each year, which is more than any other terrestrial farmed animal: chickens 66 billion, pigs 1.5 billion, lamb 588 million and beef is 290 million.

Expansion of aquaculture

The increase in demand for seafood products has not only caused rapid growth in the farming of common fish species (like salmon and seabass) but has also led to the development of farming systems for other aquatic species, such as octopus or tuna. However, different species have different biological and behavioural needs and may not be adapted to live in captivity.

close up of octopus underwater

Octopus, for example, is a carnivorous species with complex behavioural needs and farming them is not only detrimental to their welfare but will increase the pressure on wild fish stocks to provide for their feed.

Reliance on wild-caught fish as feed

trawler ship hauling huge catch net of fish

In aquaculture, many carnivorous species such as salmon are fed on huge volumes of wild-caught fish in the form of fishmeal and fish oil. The fishmeal industry accounts for 0.5-1 trillion fish out of the 0.79-2.3 trillion fish caught every year.

Over 78% of fishmeal and 68% of fish oil production is used to feed farmed animals - predominantly fish. This is inherently unsustainable as it is causing a global crisis in overfishing and depleting the food source for many local communities and wildlife including sea birds and marine mammals.

Find out more about how industrial aquaculture is plundering our oceans.

Certification schemes

There are several certifications schemes that certify aquaculture production to ensure sustainability and good practices.

However, the standards of the five key global fish certification bodies, including the Marine Stewardship Council (MSC), Aquaculture Stewardship Council (ASC), GlobalG.A.P., Friend of the Sea (FoS) and Best Aquaculture Practices (BAP), mainly focus on the environment, human rights, and for MSC and FoS, on the sustainability of fish stocks. While this is extremely important, more needs to be done to introduce standards to protect the welfare of all fish during rearing, capture, transportation and slaughter.

Many of these schemes are new to the concept of animal welfare, even though welfare is intrinsically linked to sustainability.

As part of our Rethink Fish campaign, Compassion has been urging certification schemes to ensure adequate standards for good fish welfare.

Although some of the certification bodies are now reviewing their standards to start including fish welfare requirements, this is a slow process and fish welfare is often included in a limited way.

Read more about the policies of the different labelling schemes below.

Common issues in aquaculture

Common issues in aquaculture

Fish stunning and slaughter

Fish are often killed inhumanely, and many endure slow, painful deaths caused by asphyxiation; submersion in a mixture of ice and water; exposure to carbon dioxide and bleeding, among others.

fish asphyxiating gasping

These cause considerable pain, fear and suffering and can be extremely prolonged. For example, many fish remain conscious and aware of pain for several minutes after having their gills cut and being left to bleed out.

Humane methods of slaughter do exist – British and Norwegian farmed fish are generally stunned before killing. However, stunning prior to slaughter is not mandatory under the law – and sometimes poorly practised - so there may still be millions of fish that are killed without prior stunning.

Compassion recommends that all fish are effectively stunned, rendered instantly insensible, and remain unconscious until death supervenes to avoid any suffering.

Click on the buttons to find out more about farmed fish slaughter in the EU, and how to develop a corporate policy on humane slaughter.

Humane fish slaughter policy Farmed fish slaughter in the EU

Overcrowding, water quality and rearing environment


school of salmon in intensive farm pen

Industrial aquaculture relies on rearing vast numbers of fish inland or sea-based enclosures, at high stocking densities to make production commercially viable. However, the overcrowded conditions on these farms limit the space available to the fish which curbs their behaviour and can cause aggression, leading to injuries and stress. It can also limit the ability of subordinate fish to escape more dominant ones, and even the fishes’ ability to swim.

Water Quality

poor water quality in salmon fish farm

Fish stocked at high densities require more oxygen from the water and produce more waste which can affect water quality.

In nature, fish would be able to swim away from areas of poor water quality and harmful algal blooms, but in aquaculture, they are trapped and left to suffer the effects, which include damage to and clogging of their gills and reduced oxygen levels, both of which can lead to suffocation.

Rearing environment

Barren tanks, raceways and cages are not acceptable habitats for farmed fish to have a good quality of life. Lacking any stimuli, the fish can do nothing more than swim around aimlessly in circles. However, their environment can be enriched to give the fish more environmental complexity which can, in turn, reduce stress and aggression.

Sea Bass and Sea Bream, for example, habitually sift through substrates to forage and bury themselves in the sand to hide and rest, and salmonids hide in rocks as protection against predators and bad weather.

It is important that each species of fish receives the right type of enrichment for each stage of its life, and it should be provided in the appropriate quantity and position to help decrease stress and avoid aggression.
ASC, GlobalG.A.P. and BAP do not require the provision of enrichment in their standards, although FoS recently updated their standards to recommend that structural enrichment be provided.

Producers must ensure fish are stocked at a lower density with environmental enrichment which promotes their physical and mental wellbeing, providing more space to swim, reducing stress and aggression, and allowing for better water quality.

Click on the buttons to read more about environmental enrichment for farmed fish and how MOWI's fish welfare policy includes a commitment to lower stocking densities, humane slaughter and providing enrichment for fish.

Enrichment during rearing Environmental enrichment

MOWI’s fish welfare policy

Wounds, diseases and treatments

lice infested salmon in fish farm cage

The lack of space on fish farms can lead to aggression and increase the number of wounds - for example, it is very common to see bitten fins in aquaculture. Fish frequently collide with each other and scratch themselves on the nets when they are crowded together for harvesting, grading or simply when they react to an external stressor, being that a diver, a predator, or any procedure carried out on the farm, including feeding.

Fish possess a well-developed non-specific immune system. These are the barriers that form their first line of defence: the skin (including its mucus coating), lateral line, and gills in the case of fish. Any wounds will break or remove these barriers, making way for pathogens to infect the weakened fish. Furthermore, the overcrowded conditions in aquaculture enclosures provide the perfect conditions for diseases to spread and it aids the transmission of diseases and parasites among the fish.

Salmon in fish farm suffering lice infestation and missing an eye

Sea lice infestations, for example, have become common in aquaculture, accelerated by high stocking densities, and enabling a rapid spread through the stock from one farm to the next, and even out to wild salmonids. Sea lice are parasites that feed on the skin, blood and mucous of salmonids, resulting in large open wounds which can become infected and result in death.

Diseased fish should be treated to ensure their welfare, but rampant infections like these should be prevented by better management practices. Unfortunately, many of the current practices to treat diseases fail to implement effective welfare and are often bad for the environment too:

  • Many disease treatments are used in open water in the form of chemical baths or dispersion of the medicine into the water, which means chemicals can spread out to the surrounding water and impact other fish and wildlife, and the environment.
  • Some medical treatments are added to the fish feed, yet uneaten food will often end up at the bottom of the sea where it causes algal blooms, affecting the local fauna and flora.
  • Antibiotics are often routinely used to combat disease, contributing to the increasing huge threat of antibiotic resistance.
  • In the case of sea lice, current methods used in the salmon industry include chemical baths, thermolicer (thermal shock) and hydrolicer (mechanical removal) treatments which can cause injury, stress and high mortality.
  • The use of ‘cleaner fish’ which eat the lice off the salmon is another popular treatment, but their welfare is rarely considered, and they also suffer from poor health and high mortality.

Limiting time without feed

A common practice in aquaculture is the periodical starving of fish, particularly before transport and slaughter. This ensures that their digestive systems are empty to help maintain water quality during transport and to avoid contamination with faecal matter during slaughter.

The time required for the digestive system to empty varies between species and depends on the water temperature. Usually, 48-72 hours is sufficient time to empty the gut of most farmed species. However, certification schemes permit the unnecessary prolonged starving of fish which can last for several weeks. This causes great distress, weakened fish, and can lead to aggression and serious injuries.

Farmed fish species

Farmed fish species

Atlantic Salmon

salmon leaping up stream

Also known as the “King of Fish", Salmon (Salmo salar) is one of the most reputed fish species due to the enticing images you see of them migrating upstream to spawn in rivers. Their life cycle is complex as they are anadromous fish, which can live in both fresh and seawater. In the wild, they are born in upstream rivers where they spend their early stages of life, before swimming out to sea where they mature and migrate incredible distances before returning to the rivers where they were born to spawn.

Atlantic salmon are both a sturdy and a delicate species. They can travel long distances, but they are also vulnerable to stress. They thrive in relatively cold, clean, and well oxygenated waters, in rivers that allow them to move around easily. They are found along most North Atlantic coastlines in Europe but warming waters and human pressure is taking their toll and populations are dwindling. Find out more about ‘Who is the Salmon?’.

Salmon in aquaculture

Atlantic salmon is consumed all over the world and is one of the main farmed fish species. It is produced mainly in Norway, Chile, Scotland and Canada, the majority in sea cages. Salmon aquaculture production has increased by around 70% since 2010 and is expected to grow even further due to its popularity among consumers.

Salmon suffering with sea lice infestation

In aquaculture, salmon experience high mortality caused by disease, sea lice and delousing treatments. For example, Scotland and Norway reported losses due to mortality of 13.5% and 15% of the whole yearly production (tonnes) in 2019.

Resources - Salmon

A summary illustration of the key things you need to know about salmon.

A summary about the production of Atlantic salmon and a brief description of the pack of resources available.

Science Driving Change: a literature review of the science behind the Atlantic salmon welfare framework.

This document provides recommendations for inputs and outputs to improve the welfare of Atlantic salmon during rearing.

This document provides recommendations for improving the welfare of Atlantic salmon at slaughter.

A summary of the main challenges and possible solutions in the production of Atlantic salmon.

A summary of published data related to salmon aquaculture that offers a view of the industry from production to mortality and disease through trade and consumption.

Best Practice Guidance Document: Pinniped Predator Control - discusses the issues around pinniped predation for fish farms and gives guidance on management methods to ensure high welfare for the fish and for marine life.

Infographics - Salmon

An introduction to the problems caused by sea lice and how treatments have been changing.

A summary of the issue of pinniped predators for salmon aquaculture and how it is managed.

This infographic summarises the main concerns with using RAS (Recirculating Aquaculture Systems) for salmon grow-out.

An infographic that summarises the main concerns of cleaner fish use.

European Sea Bass and Gilthead Sea Bream

Gilthead sea bream swimming underwater

Sea Bass (Dicentrarchus labrax) and  Sea Bream (Sparus aurata) form a huge part of the Mediterranean diet, yet they may be found in waters stretching from the Mediterranean right up to the North Atlantic and the North Sea. They live in coastal areas, although they tend to spend the colder months further away from the coast searching for waters with more stable temperatures.

Sea Bass and Sea Bream have similar diets, feeding on small crustaceans, molluscs and worms. Sea Bream, with their specialised mouths and teeth, are easily equipped to crush shells, so they tend to eat more crustaceans and molluscs, as well as algae and other marine plants. By comparison, Sea Bass are known to be voracious carnivores and include other fish in their diet.

Read more about each species here: ‘Who is the Sea Bass?’ and ‘Who is the Sea Bream?’

Sea Bass and Sea Bream in aquaculture

Sea Bream is a fish that changes sex during their lives. They are protandric, meaning that they are first males until they are approximately 2 years old, when they become females. This is one of the reasons why the industry is interested in harvesting Sea Bream before this happens, as females will invest more resources in developing eggs instead of growing.

European Sea Bass 540X361

Sea Bass and Sea Bream are the main fish species in Mediterranean aquaculture. Production of both species has been spearheaded by Turkey, followed by Greece, and global production has risen each year, with an increase of 75% for Sea Bass and 60% for Sea Bream between 2010 and 2018.

Both species experience a 20% mortality in aquaculture, but the cause of illness is different for each: Sea Bass tend to suffer from bacterial diseases while for Sea Bream it’s mainly parasitic diseases. Sea Bream also suffer from what is known as “Winter Syndrome” – a multifactorial pathology caused by the inability to migrate to deeper waters to avoid cold temperatures.

Find out more about the farming of Sea Bass and Sea Bream:

Resources - Sea Bass & Sea Bream

A summary illustration of the key things you need to know about sea bass.

A summary illustration of the key things you need to know about seabream.

A summary about the production of Sea Bass and Sea Bream and a brief description of the pack of resources available.

A literature review of the science behind the Gilthead Sea Bream and European Sea Bass welfare framework.

This document provides recommendations for inputs and outputs to improve the welfare of Sea Bass and Sea Bream during rearing.

This document provides recommendations on how to improve the welfare of Sea Bass and Sea Bream at slaughter.

A summary of the main challenges and possible solutions in the production of European Sea Bass and Gilthead Sea Bream.

A summary of published data to offer a view of the industry from production to housing systems.

A summary of published data to offer a view of the industry from production to housing systems.

A case study and accompanying video of how Tesco has worked with its Turkish suppliers to introduce a humane electrical stunning system for European sea bass and gilthead seabream.


Rainbow Trout

Rainbow Trout (Oncorhynchus mykiss) is a freshwater salmonid but, like salmon, they spend the first years of their lives in a river and then migrate out to sea, where they will mature before returning to the same river to breed.

Rainbow trout swimming underwater

Originally, they were found in coastal waters and rivers along the Pacific North American coast down to Mexico, and in some areas of Asia along coastlines in the Bearing Sea. Like other trout, they live in clean and cold water, but they adapt easily to environmental changes. Rainbow Trout is known as the chameleon of fish for their ability to dramatically change colour to mimic their environment, or when they feel stress or perceive danger. They are predators and their main diet is composed of insects and small aquatic invertebrates, and if the opportunity arises, they will prey on other fish or their eggs. Their taste and smell senses are 500 times more sensitive than humans, and wild Rainbow Trout have been observed playing fetch with a coin, illustrating the point that they are sentient beings with complex behaviours.

Read more about Rainbow Trout here: Who is the Trout?

Rainbow Trout in aquaculture

Rainbow trout

While they originated along the Pacific Ocean coasts, Rainbow Trout have been introduced into aquaculture across the globe and they are the most cultured trout species. Generally, they are reared in ponds, but raceways, recirculation systems and floating cages are also used.

The main producers of trout globally are Chile, Norway, Italy, France and Denmark, but the continent that consumes the most is Asia, which has increased its consumption by 62% since 2010. 

Find out more about the farming of Rainbow Trout:

Resources - Rainbow Trout

A summary illustration of the key things you need to know about trout.

A summary about the production of Rainbow Trout and a brief description of the pack of resources available.

A literature review of the science behind the Rainbow Trout welfare framework.

This document provides recommendations for inputs and outputs to improve the welfare of Rainbow Trout during rearing.

This document provides recommendations to improve the welfare of Rainbow Trout at slaughter.

A summary of the main challenges and possible solutions in the production of Rainbow Trout.


(two species: Pangasianodon hypophthalmus and Pangasius bocourti)

Pangasius swimming under water

Also known as shark catfish, Pangasius originated in the Chao Phraya and Mekong rivers in Cambodia and Thailand but they have also been introduced into rivers in Colombia for aquaculture purposes.

Pangasius are migratory freshwater fish that prefer deep, wide rivers where they can swim freely, moving from rearing areas upstream to spawn. They are omnivorous and feed on fish and crustaceans but also on vegetable matter. Pangasius feel comfortable in dark waters, thanks to their barbels that help them navigate and hunt.

Read more about Pangasius: Who is the Pangasius?

Pangasius in aquaculture

pile of dead pangasius

Pangasius is the main fish farmed in South-East Asia, Vietnam being the main producer. In 2017, between 0.86 and 2.57 billion fish were farmed which is the equivalent to approximately 1.2 million tonnes.

USA, China and the EU are the main importers of Pangasius, and although consumption has declined in the EU, Pangasius is still one of the Top 10 most consumed finfish in the EU.

Fine out more about the farming of Pangasius:

Resources - Pangasius

A summary illustration of the key things you need to know about Pangasius.

A summary about the production of Pangasius and a brief description of the pack of resources available.

A literature review of the science behind the Pangasius welfare framework.

This document provides recommendations for inputs and outputs to improve the welfare of Pangasius during rearing.

This document provides recommendations to improve the welfare of Pangasius at slaughter.

A summary of the main challenges and possible solutions in the production of Pangasius.


Common carp swimming under water

Carp are a group of fish that are native to Europe and Asia, but they have been introduced in many places as ornamental fish or for recreational fishing. They are freshwater fish that show a preference for large bodies of slow-flowing, or still water. They are omnivorous, feeding on plants and invertebrates on the riverbed.

They have a good sense of hearing and with training can learn to recognise music and demonstrate individuality as they can have different food and taste preferences.

Read more about Carp:

Global production of common Carp reached nearly 4.5 million Tn in 2019, which has increased by 32% since 2010. The main producer is China which accounts for 65% of global production.

carp gasping for air in crowded pool

In Europe, 168,000 Tn of Carp are produced each year, mainly in Eastern European countries like Poland where they have a tradition of eating carp at Christmas. Unfortunately, this has led to the selling of live carp on the lead up to Christmas which causes unnecessary suffering to the fish: live carp are often transported to stores in overcrowded tanks and then crammed into huge commercial pools which affects the oxygen in the water and leads to aggression. After purchase, they then suffocate in water-free plastic bags, to be later killed at home by unqualified people.

Compassion has been calling for a ban on the sale of live carp for years. Find out more from our Polish team.

Nile tilapia

Pangasius swimming under water

Nile tilapia, very often referred to simply as tilapia, is a fish commonly found in the Nile river system, central Africa and the Mediterranean Middle East, from where they have been introduced to Asia and Central and South America. They are mainly freshwater fish although they are capable of living in brackish water found in locations such as deltas and coastal lagoons. This species is used to living in an environment with a high degree of structural elements such as branches, plants and floating matter, that allow them to find refuge and feed safely. They are opportunistic in behaviour, meaning that they will eat plants, plankton, insect larvae and detritus, depending on what is most prevalent and its life stage.

Unlike many other fish species, Nile tilapia is known to display parental care. The females provide refuge to their offspring in their mouth whenever a threat is perceived. Their breeding behaviour is also notable; they are known to use sound to communicate the whereabout of their territories, and colour for mating.

They are cichlids, and as such, they are closely related to some popular aquarium fish. Tilapia farming goes back decades and dates back to Ancient Egypt, where the fish are represented in hieroglyphs and Egyptian art.

Nile tilapia in aquaculture

In 2021, the farming industry of Nile tilapia reached nearly 5 million tonnes, the equivalent to approximately 9-14 billion Nile tilapia, making them the third most farmed finfish worldwide by number of individuals - nearly 21 times the number of Atlantic salmon farmed.

This species is consumed worldwide, and 93.4% is farmed. The farming and consumption of Nile tilapia is found mostly in Asia and Africa, and more specifically the main countries farming Nile tilapia are China, followed by Indonesia and Egypt. Many countries import tilapia, but the main importer worldwide is the United States of America, with China as the main exporter. Although Indonesia and Egypt are big Nile tilapia farmers, most of their production is for their own consumption.

Nile tilapia is a good candidate for more sustainable aquaculture, due to their low trophic profile, and they have a higher welfare potential than other species. It is possible that rearing tilapia in ponds with a low stocking density may meet their behavioural needs,  and they can be fed on the pond's natural production  without relying on external feed.

Resources - Nile Tilapia

A summary illustration of the key things you need to know about Nile Tilapia.

A summary about the production of Nile tilapia, a brief description of the pack of resources available and a summary of Compassion's Corporate Asks for this species.

A summary of the main challenges and possible solutions in the production of Nile tilapia.

This document provides recommendations for inputs and outputs to improve the welfare of Nile tilapia during rearing.

A literature review of the science behind the Nile tilapia welfare framework.

This document provides recommendations to improve the welfare of Nile tilapia at slaughter.

Other aquatic species

Other aquatic species


octopus close up

Octopus are cephalopod molluscs, easily identified by their eight tentacles. They can be found in marine habitats far and wide, from tropical reefs to the polar latitudes. They are a mostly benthic species, meaning that they trawl the bottom of the sea where they hunt at dusk for crabs, crayfish, and bivalve molluscs, in an area centred around their den where they can shelter from predators.

Octopus are well reputed by their skin changing abilities, changing colours to mimic their environment and to communicate. They can not only change colour but also the texture of their skin.

octopus on rocks in marine environment

Octopuses display extraordinary intelligence and are very inquisitive, continually exploring their surroundings. They present a variety of complex behaviours and have, for example, been known to cover themselves in shells or coconuts to hide from predators.

Asia is the main region that fishes for wild octopus, and Korea and Spain are the biggest importers. As wild octopus are being overfished and their numbers have been decreasing, the price of octopus has risen which has increased the interest in farming them.

Octopus in aquaculture

Although there is no aquaculture production of octopus to date, the industry is currently exploring ways to farm them, and it has been announced that Spain will start commercialising their production by 2023.

Octopus are, however, carnivorous species with complex behavioural needs so farming them on land would not only be detrimental to their welfare but will also increase the pressure on wild fish stocks needed to feed them.

Read more about the pitfalls of Octopus farming.

Issues of Octopus farming Octopus farming problems


small red shrimp on rocks

Shrimp are a variety of decapod crustaceans which inhabit most coasts and estuaries, as well as rivers and lakes, scavenging for algae, bacteria, and other microorganisms, including decaying organic matter. Generally, they are solitary except during the spawning season when they can form large schools.

whiteleg shrimp on conveyor belt

The Whiteleg shrimp, native to Sonora in Mexico, is the species that is mostly used in shrimp farming, with a production of 5,446 million tonnes in 2019, which has doubled since 2010. Whiteleg shrimp were introduced in Asia at the beginning of the millennium and Asia is now the biggest producer.

Read about our Corporate Asks and our Review supporting them here: Whiteleg Shrimp - Corporate Ask

Tesco and Hilton SeaFood - Improving the Welfare of Whiteleg Shrimp (Pennaus Vannamei) at Harvest

Tesco and Hilton SeaFood have worked together to improve the Welfare of Whiteleg Shrimp (Pennaus Vannamei).

It is the first, large scale electrical stunning system of its kind designed for the humane slaughter of hundreds of millions of prawns in the Tesco supply chain. 

Get in Touch

Compassion will continue to work with industry to improve the welfare of farmed fish and other farmed aquatic species through it's various corporate engagement programmes.

If you want more help or information, please contact the Food Business team.


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If you have any further questions regarding this, or any other matter, please get in touch with us at We aim to respond to all queries within two working days. However, due to the high volume of correspondence that we receive, it may occasionally take a little longer. Please do bear with us if this is the case. Alternatively, if your query is urgent, you can contact our Supporter Engagement Team on +44 (0)1483 521 953 (lines open Monday to Friday 9am to 5pm).