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Undercover investigation

Agony Underwater

AnimaNaturalis presents its investigation exposing the reality of fish farms in Spain, where an immense number of animals suffer every day without any specific regulations to protect their basic interests. Since we cannot hear their screams and their agony is drowned underwater, they seem invisible.

More than 30 million rainbow trout are raised for consumption, representing 70% of freshwater fish in such facilities. The stress they endure is constant: fights over food, injuries and slaughter without effective stunning. Spain is the EU’s leading producer and is responsible each year for over 254 million fish—both marine and freshwater—without any national welfare legislation.

To change this reality, we propose drastically reducing or eliminating fish consumption and choosing plant-based alternatives, while urgently elevating the legal protection of fish to the level of other farm animals.

Undercover investigation on fish farming. Spain, 2025.

What fish farms hide

Breeding and fattening

In fish farms, trout undergo a wholly artificial reproduction cycle: they are anesthetized to manually extract eggs and milt, the fry spend their first weeks in enclosed tanks, and then compete in densely stocked tanks, causing chronic stress and depriving the fish of any natural stimulation. Their fattening, which lasts between 9 and 20 months, relies on processed feeds that neither satisfy their dietary needs nor replicate the variety of prey in their habitat, and is adjusted to the pale flesh demanded by the market. Additionally, intensive breeding consumes up to five kilos of wild fish for every kilo of trout produced and reduces their lifespan from up to 10 years in the wild to barely one or two.

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Overcrowding

Overcrowding raises chronic stress in fish, spiking cortisol levels and triggering the breakdown of muscle proteins, which reduces their growth and body mass. Moreover, the immune system weakens, increasing vulnerability to diseases, while physical wear—such as fin erosion and scale loss—and stereotypical behaviors become more frequent. High stocking density also degrades water quality: it lowers available oxygen and raises toxic ammonia due to increased waste excretion, fostering aggression and competition for food, as dominant individuals monopolize feed and marginalize others, further amplifying stress and injuries within the group.

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Sorting

Trout sorting often uses suction machines that rapidly vacuum fish to separate them by size. This method causes violent handling that leads to bruising, fin and scale damage, and elevated cortisol from stress. In smaller facilities or alternative methods, manual or mechanical nets entangle fish, causing friction wounds and exposing them to air for several minutes. If out of water for more than 15 seconds—unless anesthetized—they suffer asphyxiation and disorientation, and may fall, collide, fracture bones, or even die. All in pursuit of speed and low cost, disregarding animal welfare.

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Transport

Transporting fish to the slaughterhouse—often in live tanks on boats or water containers—subjects them to low oxygen levels that reduce activity and cause high stress. Overcrowding in these containers creates anxiety and erratic movements, increasing the risk of bruises and abrasions from crowding. Moreover, lack of strict water quality control during transit can elevate ammonia levels, further worsening the suffering. Rough handling when loading and unloading containers contributes to physical injuries and extends stress until slaughter, making their final life stage particularly traumatic.

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Cold and Electrical Slaughter

The most common method in fish farms is thermal shock: fish are submerged in ice or ice-slurry water for up to 90 minutes, suffering hypothermia and asphyxiation agony while conscious for much of the time. Although economical, this system causes prolonged suffering as their gills fail under the cold. Electrical stunning is offered as a “more humane” alternative, but poorly calibrated shocks often leave many fish semi-stunned and conscious during gutting, displaying agonizing movements and breathing difficulties, violating Regulation (EC) 1099/2009, which prohibits causing “avoidable pain, distress or suffering.”

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Percussion Slaughter

Percussion, considered effective if applied correctly, suffers high error rates due to mechanical failures or improper manual handling, leaving fish conscious during cutting or decapitation. Additionally, pre-slaughter fasting—allowed up to six days before killing to improve hygiene—weaken the trout’s immune system, induce behavioral stress, and increase intra-species aggression, counteracting the goal of minimizing suffering. Overall, the lack of specific welfare regulations in Spanish fish farms allows these cruel methods to persist, underscoring the urgent need for reforms to ensure truly painless slaughter.

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Diseases

Diseases in rainbow trout farms arise directly from stress and overcrowding: bacterial enteritis and furunculosis cause skin ulcers and high mortality; parasites (Argulus, Lepeophtheirus) damage skin and gills and spread rapidly; and viruses like Infectious Pancreatic Necrosis (IPN) trigger massive outbreaks requiring mass antibiotic and antiparasitic treatments. Under Regulation 2016/429, most of these diseases are not notifiable, lack standardized veterinary protocols, and have unreliable epidemiological data, hindering control and worsening fish suffering.

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Diseases

Diseases in rainbow trout farms arise directly from stress and overcrowding: bacterial enteritis and furunculosis cause skin ulcers and high mortality; parasites (Argulus, Lepeophtheirus) damage skin and gills and spread rapidly; and viruses like Infectious Pancreatic Necrosis (IPN) trigger massive outbreaks requiring mass antibiotic and antiparasitic treatments. Under Regulation 2016/429, most of these diseases are not notifiable, lack standardized veterinary protocols, and have unreliable epidemiological data, hindering control and worsening fish suffering.

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Antibiotics

Extensive antibiotic use in aquaculture promotes resistance affecting human and animal health—the residues can reach consumers—and antiparasitics and other chemicals contaminate water and soil. Additionally, plastics, oils, and sanitary waste from fish farms harm aquatic biodiversity, alter water quality, and disrupt food chains. The “Strategic Guidelines for Sustainable Aquaculture 2021–2030” report by MAPA acknowledges disease as a production limitation and welfare issue, while the industry admits the lack of epidemiological studies and the challenge of controlling widespread epizootics.

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Packaging

Packaging prolongs trout suffering, as many still show vital signs after slaughter and chilling when placed in transport boxes. When stacked carelessly, some fish are asphyxiated or crushed, reflecting grave post-mortem handling negligence.

This stage highlights the absence of specific regulations guaranteeing fish welfare until the last moment, allowing abuse to continue even when they are destined for market.

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Minimum and Urgent Welfare Requirements for Fish

We can conclude that the current state of aquaculture in Europe presents serious shortcomings in terms of animal welfare. Fish, despite being the most exploited vertebrate animals in the world, are subject to far less stringent regulations than other animals raised for consumption. This analysis, supported by the opinions of our own organization and allied groups in the Eurogroup for Animals coalition, reveals a precarious and urgent situation.

The ten proposals we present below do not aim to achieve an optimal welfare standard, but rather to establish the absolute minimum requirements to ensure basic conditions of living, handling, and slaughter that should be taken into account in the upcoming Good Practice Code for Fish Welfare being developed by the European Commission.

We know that these measures, while necessary, are insufficient to deliver real welfare. However, they represent a first step toward equating fish rights with those of other farmed animals and are essential to begin correcting the current regulatory disparities.

Implementation of effective stunning methods for all fish species, ensuring immediate loss of consciousness before slaughter. Methods such as properly applied electrical stunning and controlled hypoxia are highly recommended, while air asphyxiation, bleeding without prior stunning, thermal shock in ice, or the use of carbon dioxide should be prohibited due to the cruelty involved.

Overcrowding in cages and ponds generates chronic stress in fish, weakening their immune systems and increasing disease spread. Limiting fish density is essential to allow natural behaviors, reduce aggression, and improve water quality. Regulations must specify clear limits by species and environmental conditions, tailored to each fish's biological needs.

Housing must meet fish welfare needs, allowing them to exhibit their natural behaviors as much as possible. Appropriate substrate and shelter must be provided for different species.

Fish welfare is directly linked to the water quality they live in. Parameters such as dissolved oxygen, temperature, pH, and ammonia levels must be kept within specific ranges to avoid stress and disease. The use of automated systems for continuous monitoring and alerts for sudden changes is recommended. Moreover, rapid response protocols must be in place to correct issues that could affect fish welfare.

Transport is one of the most stressful stages for fish, due to factors like handling, temperature fluctuations, and reduced oxygen. It is proposed to limit the maximum travel time, set standards on water volume per fish, and require vehicles equipped with oxygenation and temperature control systems.

Handling of fish, especially out of water, should be minimized. Methods such as using dry nets (for transport, slaughter, treatments, farm transfers, or other purposes) must be avoided.

Practices such as tagging, fin clipping, and evisceration are often performed without anesthesia, causing avoidable pain and suffering. We propose banning these procedures without the use of appropriate anesthetics and techniques that minimize pain.

Require specific training for workers in respectful handling techniques, identification of stress signs, and the use of technologies that minimize fish suffering.

Create a set of specific indicators, such as growth rates, mortality, abnormal behavior, and stress response, to objectively assess fish welfare. These indicators must be measurable and adapted to each species, with mandatory monitoring in all fish farms.

Implement frequent inspections by independent bodies to verify compliance with animal welfare regulations at all aquaculture facilities, covering every production stage from handling to slaughter. Inspection reports must be public to ensure transparency.

The industry must invest in research projects aimed at developing new technologies and methods to improve fish welfare, especially regarding handling and slaughter, and promote studies on species-specific behavior and needs, facilitating the adoption of more ethical and efficient practices.

Establish a clear and transparent labeling system to inform consumers about the level of animal welfare in fish product production, encouraging more ethical practices and enabling consumers to make informed and responsible choices. This labeling must be verifiable, regulated by independent entities, and accurately reflect the conditions under which fish are bred, handled, and slaughtered.

Regarding transparency, competent bodies should also count fish in fisheries and aquaculture production by number of individuals rather than tons, and periodically collect and publish data on welfare indicators including disease incidence and mortality rates.

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