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Aquaculture today: how do we treat the fish we eat?

By Juliette ALEMANY, January 2021

Over the past 60 years, in parallel with the increase of wild catch fisheries and eventually the decline of wild fish population abundance, aquaculture has grown exponentially. It has raised several environmental concerns, with an increased consumers’ awareness about environmental and social issues.


The increasing demand for food produced in a sustainable way resulted in the creation of international standards that ensure the respect of strict requirements for sustainable farming practices. While the environmental and social aspects are usually well scrutinized, there is still little emphasis on the animal welfare.


The pressure experienced by bovine or poultry producers regarding animal welfare is still much higher than aquaculture producers. Yet animal welfare, productivity and environmental sustainability are closely linked in aquaculture, and awareness around these issues is growing.

Box of Fresh Fish


Do fish experience pain the same way we do?

Fish express pain differently from birds or mammals: they don’t shout when they suffer. Human often relate more to mammals than to fish, which explains why the awareness towards fish welfare was greatly delayed compared to the attention allocated to other species. Furthermore, fish dying onboard fishing vessels far from the coast were of little concern for consumers who could not really picture what was happening there. There have also been some assumptions that fish did not have a conscious and could not feel pain based on the absence of neocortex in the brain, which among humans allows the awareness of pain (Rose 2002).

In order to evaluate the level of stress and pain in aquatic animals, researchers use various methods including behavior observation and measures of different indicators in muscle tissues or in blood like lactic acid, pH, cortisol, plasma glucose, etc. Various researchers have studied fish behavioral and physiological response to painful events and concluded that fish do experience pain as the responses are more than just reflexes (Sneddon 2006; Chandroo, Duncan, and Moccia 2004).


What are the main causes of decreased animal welfare in aquaculture?

Overcrowded ponds, bad water quality and unethical slaughter techniques are among the most common threats to aquatic animal well-being. High stocking densities induce higher risk of parasite infestation, which can result in higher mortality rates. Crowded ponds can also hinder normal swimming patterns and alter animal behavior, inducing aggressive behaviors that result in long term stress and injuries (Wedemeyer 1997).

Fish are very sensitive to temperature increase as it induces higher metabolic rates and increases oxygen needs (Webster 2011). On the other hand, if the water temperature drops below the ideal range for a specific species, a negative impact can occur on feeding and on the immune system (Lemly 1996). When water quality deteriorates, aquatic animals are more at risk regarding bacterial infection and blood infection (Wedemeyer 1997).

The transport phase can be a big source of stress for aquatic animals. In water containers used for the transport, the water quality can rapidly deteriorate as the amount of water is limited. It can happen that animals are transported to the slaughtering location without water and therefore suffer from suffocation before being killed.

The slaughter technique is the next important source of impaired animal welfare. Techniques involving long periods of suffering before death occurs are still widely used. One of the most common technique is probably air suffocation, where the fish is left out of the water to die slowly because of the inability to get oxygen in the body. Another common method is the exsanguination where the gills are cut and the animal is left in the water to die from the loss of blood. These methods induce a slow and painful death.


How can animal welfare be improved in aquaculture? What are we doing at VerifiK8?

In aquaculture, animal welfare and productivity are closely related. Farming practices that are non-harmful for the environment usually correlate with better animal welfare. To a larger extent, stressful slaughter practices result in poor meat quality. It is therefore beneficial for producers to work on the improvement of animal welfare.

Some slaughter methods are considered more ethical than others. For example, percussive and electric stunning before slaughter is commonly accepted as causing less pain to the aquatic animal because it remains insensible for a certain time. It is also important to adapt the slaughter technique to the species. For example, the use of ice bath would induce significant pain to cold water species as the death would take time to occur, whereas this technique could be well adapted for tropical species.

From the consumers’ perspective, awareness around aquatic animal welfare is rising and will probably increasingly guide consumers’ choices in the future. International standards for aquaculture are already taking steps towards the inclusion of animal welfare metrics.

At VerifiK8, we work together with farmers to support them to achieve higher social goals and farming practices that are less harmful for the environment. Through the data collection process, we already verify the stocking density, the feeding, the water quality of the ponds, and we monitor diseases outbreaks. Our goal in the near future is to include additional verification items on transport, slaughter methods, and potential painful farming practices. For example in shrimp aquaculture, many farmers still apply the method of eyestalk ablation. This practice consists in removing one or two eyestalks of the female to induce ovarian maturation and therefore achieve more frequent spawning.

v8 logo fish.jpg

There is still a lot to be done to improve animal welfare in aquaculture, and this goal can only be achieved with all involved stakeholders working together. An increasing number of NGO is working on this topic, and consumers’ awareness is driving changes. Hopefully, tomorrow’s aquaculture will follow much more ethical rules and we will be able to buy fish with a clean conscience.

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Literature cited

Chandroo, K. P, I. J. H Duncan, and R. D Moccia. 2004. “Can Fish Suffer?: Perspectives on Sentience, Pain, Fear and Stress.” Applied Animal Behaviour Science, International Society for Applied Ethology Special Issue: A selection of papers from the 36th ISAE International Congress., 86 (3): 225–50.


Lemly, A. Dennis. 1996. “Winter Stress Syndrome: An Important Consideration for Hazard Assessment of Aquatic Pollutants.” Ecotoxicology and Environmental Safety 34 (3): 223–27.


Rose, James D. 2002. “The Neurobehavioral Nature of Fishes and the Question of Awareness and Pain.” Reviews in Fisheries Science 10 (1): 1–38.


Slater, M, E Fricke, M Weiss, A Rebelein, M Bögner, M Preece, and C Radford. 2020. “The Impact of Aquaculture Soundscapes on Whiteleg Shrimp Litopenaeus Vannamei and Atlantic Salmon Salmo Salar.” Aquaculture Environment Interactions 12 (April): 167–77.


Sneddon, Lynne. 2006. “Ethics and Welfare: Pain Perception in Fish.” Bull. Eur. Ass. Fish Pathol 26 (January).


Webster, John, ed. 2011. Management and Welfare of Farm Animals: UFAW Farm Handbook. 5th ed. Wheathampstead, Herts, UK: Universities Federation for Animal Welfare.


Wedemeyer, Gary. 1997. “Effects of Rearing Conditions on the Health and Physiological Quality of Fish in Intensive Culture.” In Fish Stress and Health in Aquaculture, 35–72. Cambridge University Press.

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