The zoologist Jordi Casamitjana looks at why vegans do not eat fishes, and nobody else should do either.

It took me completely by surprise.

I had eaten food with pieces of them for decades, but not until I was in my 30s that I first looked at their face. About 20 years ago, I was a vegan freelance investigator, and the Captive Animals’ Protection Society (now called Freedom for Animals) hired me to do some undercover work in UK public aquaria. It involved going into many aquaria in the country with both a handheld video camera and a concealed camera and investigating what happened to the animals there. I had to investigate all of them (not just the ones who were bigger and easier) so I spent a considerable time looking at them trying to detect any abnormal behaviour that would illustrate the ordeal they were experiencing while being kept captive, away from their natural home.  

While doing so, at one point I met my first live cod (demersal fishes of the genus Gadus) in an aquarium tank, and what I saw took me completely by surprise. These fishes I had eaten so many times when I was young not only had very inquisitive eyes that made them look more like a human than other fishes, but their behaviour was also very human-like, looking curiously through the glass to see who was watching them on the other side. Up to then, I had recorded many fishes performing behaviours in the tanks (often stereotypic behaviours, such as pacing, circling, or spiralling, that indicated they were suffering as much as terrestrial wild animals suffer in zoos), but not until then I saw one actually looking at me (the photo at the end of this article is a capture of the video I took), and studying me as much as I was studying him. Very soon, in one of those cosmic ironies, who had been my favourite fishes to eat before I was vegan had become my favourite fishes to look at when alive in the water — although it was very sad to see them captive.

Not that I had any doubts, but by bringing me close to them face to face, that investigation confirmed what I already knew for some time: fishes are as sentient as you and I, and just happened to be “people” who, for living in such as alien medium to us, we have failed to recognise such sentience for far too long. Unfortunately, many people out there still treat fishes as if they do not feel pain or have emotions. I am not talking about anglers and fishermen who kill them, because they, as hunters and shooters, might have lost the capacity to empathise with others — perhaps stripped off them when they were very young by irresponsible parents. I am not talking about the average meat eaters either, who would eat animals of all sorts, even when they know they had to suffer for them to satisfy their perverted taste. No, I am talking about the pescatarians, those people who already know it is wrong to eat the flesh of sentient beings (and this is why they don’t eat meat from terrestrial animals), but somehow, they feel it is OK to eat the flesh of fishes. They have rationalised this cognitive dissonance by saying to themselves that “fishes don’t matter.”

There even are people who say they are vegan and still eat fishes, believe it or not. Considering that, in terms of numbers, fishes are the vertebrates most killed and abused by humans, and that almost all of those killed for food die a long and agonising death by suffocation (who hasn’t seen a fish gasping for oxygen when taken out of the water) this is shocking to me. For instance, Eric L. Adams, the current mayor of New York City who so many people — including us — celebrated for being the “First Vegan Mayor in New York City’s History”, was later caught eating fishes, to which he replied, “I want to be a role model for people who are following or aspire to follow a plant-based diet, but as I said, I am perfectly imperfect and have occasionally eaten fish.”

It seems that, after all, we may need to write an article explaining why vegans don’t eat fishes.

Fishes Are Not What They Seem

Coelacanth, a living fossil fish By AlessandroZocc via Shutterstock (Royalty-free stock photo ID: 120947770)

The strange thing about fish is that they do not exist as such. Well, of course they do as individuals, but the term “fish” lumps many creatures together that are very different to each other whilst they are not scientifically classed together under a single name. For us, living out here in the air-land, they all may seem just aquatic slippery-longish-scaly-finned-creatures and we call them all fishes, but although vertebrates are neatly classified into the classes amphibians, reptiles, birds, and mammals, the “fifth” class that everyone assumes is the one for fishes does not exist. Instead, fishes are typically divided into three major groups: superclass Agnatha (jawless fishes), superclass Chondrichthyes (cartilaginous fishes), and superclass Osteichthyes (bony fishes). 

Agnatha are jawless fishes who have gills in pouches and lack limb girdles. They include two classes: Myxini (hagfish) and Hyperoartia (lampreys). Hagfish are eel-like marine scavengers who produce slime and can tie themselves into knots. Lampreys are also eel-like and are found in cool, fresh, and coastal waters of all continents except Africa; they have a suctorial oral disk bearing horny teeth and seven pairs of external gills.

Chondrichthyes have a cartilaginous skeleton (they do not have hard breakable calcareous bones like birds, reptiles, or mammals), their skin is covered with placoid scales, and they lack a swim bladder. They are divided into two classes: Elasmobranchii (sharks, rays, skates, and sawfish) and Holocephali (chimaeras). Elasmobranchii has 5-7 pairs of gill clefts not covered by a fold of skin, opening separately to the exterior, while Holocephali have a single gill cover that hides four-gill arches.

Osteichthyes have a bony skeleton like ours and a swim bladder, and most fishes people know are part of this superclass, which is divided into two classes: Sarcopterygii (lobe-finned fish) and Actinopterygii (ray-finned fish). Sarcopterygii (which include primitive-looking creatures like the coelacanth and the lungfish) are characterized by their lobe-fins, which have a fleshy base and are supported by bones (amphibians evolved from fishes of this group, so we can say we also did, as we evolved from amphibians). Actinopterygii are characterized by their ray-fins, which are webs of skin supported by bony or horny spines (most non-sharky fishes people know belong to this class, from the small goldfish or the cute horsefish to the huge sunfish or the weird anglerfish).

So, as you can see, the “fifth” missing class of vertebrates who we call fishes are in fact six different classes (Myxini, Hyperoartia, Elasmobranchii, Holocephali, Sarcopterygii, and Actinopterygii) whose individuals are as different to each other as mammals are different to birds or reptiles.

What do they all have in common, though? They are all aquatic vertebrates who have gills for breathing and fins for swimming, that’s it (amphibians, reptiles, birds, and mammals are terrestrial vertebrates — or at least they were before some returned to the water — who have lungs for breathing and legs for walking — or at least they had before they lost them or modified them for other purposes).

The other thing to say at this point about fishes is that if you see one fish, you can say that was one fish; if you see two, you can say those were two fishes; if you see three, three fishes, etc. I know that in standard English the plural of fish is also fish, but I find this rule speciesist and carnistic, so I am not going to follow it. People in a carnist world have developed language that reflects their supremacism and speciesism, so when they refer to collective nouns of animals they use for food or other purposes, they tend to eliminate the forms that remind us that they are individuals. For these people, a group of cows are no longer several individual cows, but they call them cattle or livestock, as if the individuals do not matter. For them, a group of sheeps are no longer several sheeps but just a lump of sheep. And the same goes for fishes. Well, we vegans do the opposite. We never forget the individuals, so we use plurals that reflect this. So, in this article, none of the “fishes” you see are grammatical errors. They are deliberate expressions of veganised language.   

We do not lump together fishes into tonnes of food as the animal agriculture industry (and governments) do, and we should not lump them together into a discarded fake “class” of “lower” vertebrates who do not matter enough to be taught separately at school. We treat them as individuals belonging to equally distinctive and evolved groups who deserve the same respect we give to individuals belonging to any species of mammal such as us, Homo sapiens. And that is the first reason why vegans don’t eat fishes. Vegans don’t eat animals, and the Myxini, Hyperoartia, Elasmobranchii, Holocephali, Sarcopterygii, and Actinopterygii are all classes of animals of the subphylum Vertebrata of the phylum Chordata. 

The official definition of veganism finalised by the Vegan Society in 1988 is clear, “Veganism is a philosophy and way of living which seeks to exclude—as far as is possible and practicable — all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of animals, humans and the environment. In dietary terms, it denotes the practice of dispensing with all products derived wholly or partly from animals.” So, vegans should not be eating fishes, should not be taking fish oil supplements (looking for a boost of Omega-3 fatty acids), and should not be drinking beer or wine that has been clarified with isinglass (dried fish swim bladders) — but don’t worry, some vegan wines and beers aren’t.

The Sentience of Fishes

Surprised goldfish with wide open mouth and big eyes in a fishtank, By Noheaphotos via Shutterstock (Royalty-free stock photo ID: 1332341678)

The second most important reason why vegans don’t eat fishes is very much linked to the first one: fishes are sentient beings. One of the fundamental axioms of the philosophy of veganism is that all animals should be regarded as sentient, which means that they have the capacity to have positive and negative experiences by processing information with their nervous systems, obtained from their senses perceiving their environment, and they can act accordingly by moving their bodies. However, this “should be regarded” is backed by the fact that over 99% of animal species are, indeed, composed of sentient beings (the only exception being the sea sponges, proto-animals who belong to the Animal Kingdom but they have not developed a nervous system or the capacity to move yet). Even sedentary molluscs such as mussels and oysters are sentient, as I have argued in another article. If invertebrates are sentient (and there is wide acceptance of this in the case of octopuses), of course all classes of fishes would also be. However, frustratingly, there are still people out there, some with science degrees, who, for some mysterious reason — perhaps because fishing is their hobby — are still expressing doubts, so I would have to provide some evidence.

Fishes are sentient animals capable of experiencing pain and suffering, and scientific evidence supporting this has been building for years and is now widely acknowledged by leading scientists across the world. Fishes have highly developed senses, including taste, touch, smell, hearing, and colour vision, to be able to perceive their environment, one of the prerequisites of sentience. 

Fishes from all classes, even the most parasitic ones, can move — and can move faster than humans — so they can react to the positive and negative experiences their brains create after processing the information their nervous system has captured with their senses. Having such a system is another prerequisite of sentience, and although some people erroneously claim that only central nervous systems with brains can lead to sentience, there is no doubt that all fishes, from the Myxini to the Actinopterygii, as the vertebrates they are, do have a central nervous system with a well-developed brain. Not only fishes can move, but they are also capable of performing complex behaviours and are as intelligent as any other animal, as they can use their brains to resolve the problems that are relevant to them (which is the only fair way to measure intelligence).

The sentience of fishes has already been internationally recognised. The World Organisation for Animal Health (OIE) states that “The use of fish carries with it an ethical responsibility to ensure the welfare of such animals to the greatest extent practicable.” 

The 2020 version of the Guidance for the Euthanasia of Animals of the American Veterinary Medical Association stated, “Learning and memory consolidation in trials where finfish are taught to avoid noxious stimuli have moved the issue of fish cognition and sentience forward to the point where the preponderance of accumulated evidence supports the position that finfish should be accorded the same considerations as terrestrial vertebrates in regard to relief from pain” (they mean by finfish “fish that are not shellfish”). 

In the European Union, the AHAW, a scientific panel on animal welfare working for the EU Commission, recently adopted its general approach to fish welfare and the concept of sentience in fishes. Having examined the research that has been done for some species of fishes where this subject has been studied, this panel concluded the following: “The balance of the evidence indicates that some fish species have the capacity to experience pain” and that “Responses of fish, of some species and under certain situations, suggest that they are able to experience fear.” 

Dr Donald Broom, from the Department of Veterinary Medicine, University of Cambridge, UK, stated the following:The evidence of pain and fear system function in fish is so similar to that in humans and other mammals that it is logical to conclude that fish feel fear and pain. Fish are sentient beings.”

In addition to their capacity for experiencing pain and fear, fishes also show social intelligence. Studies have shown that they pursue strategies of social manipulation, punishment, and reconciliation, exhibiting stable cultural traditions, and cooperating to inspect predators and catch food. Because animal consciousness cannot be measured directly, animal welfare scientists look for anatomical, physiological, and behavioural evidence as indicators of sentience or suffering, and there is plenty of it. In particular, evidence in the form of pain receptors and appropriate behavioural responses to painful situations. 

Fish Feel Pain Just Like We Do

Rainbow trout in crystal-clear water with sun in the background by benny337 via Shutterstock (Royalty-free stock photo ID: 1830394559)

Although, theoretically, you could be sentient and not feel pain (you could have negative experiences without having localised sharp pain created by pain receptors), fishes, like all other vertebrates, feel pain as we do. There is plenty of evidence to prove it, and lots of research have done so at the highest scientific standard — although most are unethical research because it was done causing pain to animals, which could have been avoided if the entire scientific community would have applied common sense and recognise what is obvious to most of us by just observing the fishes in the wild. Following are some examples:

Many animals have sensory receptors called nociceptors that detect potential harm and produce opioids that relieve suffering. In 2002, Dr Lynne Sneddon was the first scientist to conclusively prove that fishes do have nociceptors in their mouths. In her 2003 paper titled “Do fishes have nociceptors? Evidence for the evolution of a vertebrate sensory system” published by the Proceedings of the Royal Society of Biological Sciences, Dr Sneddon and her colleagues were the first to characterize nociceptors that detect painful stimuli on the head of a fish and have since investigated the capacity for pain, fear, and stress in fishes and other aquatic animals.

Ashley et al. (2009) found that noxious stimulation affects antipredator responses and dominance status in rainbow trout, Oncorhynchus mykiss. Nordgreen et al. (2009) proved that goldfish felt both initial sharp pain and the lasting pain that follows when they studied two different doses of morphine on the thermal threshold and post-test behaviour in goldfish. Mettam et al. (2011) found that three types of analgesic drugs were effective in reducing pain in rainbow trout. Caio Maximo (2011) found that the responses of 132 zebrafishes to painful experiments suggest that they feared the events and their fear overrode their pain. 

A 2018 article from Ferris Jabr for the Smithsonian Magazine says the following: “Fish demonstrate pain-related changes in physiology and behaviour that are reduced by painkillers, and they show higher brain activity when painfully stimulated. At the anatomical level, fish have neurons known as nociceptors, which detect potential harm, such as high temperatures, intense pressure, and caustic chemicals. Fish produce the same opioids — the body’s innate painkillers — that mammals do. And their brain activity during injury is analogous to that in terrestrial vertebrates.”

A 2019 review carried out by Dr Lynne Sneddon at Liverpool University shows there is now very little doubt that fishes do experience pain. Titled “Evolution of nociception and pain: evidence from fish models” it concluded the following: “Studies in fish have shown that the biology of the nociceptive system is strikingly similar to that found in mammals. Further, potentially painful events result in behavioural and physiological changes such as reduced activity, guarding behaviour, suspension of normal behaviour, increased ventilation rate and abnormal behaviours which are all prevented by the use of pain-relieving drugs. Fish also perform competing tasks less well when treated with a putative painful stimulus. Therefore, there is ample evidence to demonstrate that it is highly likely that fish experience pain and that pain-related behavioural changes are conserved across vertebrates.”

Even those stubborn scientists who argued that the experience of pain in fishes does not equate to human-like suffering because the part of the brain responsible for such experience is very different in fishes, have now had their arguments weakened. In 2021, Phil Halper et al. wrote an article titled “Against Neo-Cartesianism: Neurofunctional Resilience and Animal Pain” pointing out that modern neuroscience research concludes that the pain effect and awareness can still be present in humans even when pain-processing regions of the brain are injured, which is helping to debunk the myth that fishes cannot feel pain if they lack the same brain regions. The researchers argue that if human brains can adapt to do without a part of the neural pain chain, then maybe fishes don’t need all of the links either. 

Fishes feel pain, as you would expect, so vegans would not do anything to hurt them, including piercing their mouths with hooks, taking them out of the water, hitting them or cutting them with blades, and, of course, killing them themselves, or paying someone to do that for them. This is why vegans don’t eat fishes.

Fishes Are Friends, Not Food

Garibaldi fish By Michael Bogner via Shutterstock (Royalty-free stock photo ID: 347217890)

If you are a pescatarian who has read this article to this point, by now you may have realised that your rationalisations for not eating pigs, cows, chickens, or turtles, but still eating salmons, sardines, cods, or tuna fishes don’t hold water — pun intended. However, if you need something more, perhaps you should look at different fishes in the wild (like in a documentary or snorkelling in your nearest water body) and see what sort of lives they live. You will then see that, once you take into consideration their natural environment, they actually live very similar lives to ours, preoccupied with mostly the same issues and reacting basically in the same ways we do. You will learn what the fishes perceive, feel, think, and ultimately what they know.  

This is precisely what the vegan ethologist Jonathan Balcome did, and he wrote it all in his 2017 book “What a fish knows: the inner lives of our underwater cousins”. I had the privilege to interview him for an article I wrote about him, and this is what he said about why he wrote about fishes: “I really like to try to help the most misunderstood, the most downtrodden, the most abused and maligned by humans. When I thought of writing a book about fishes it was like an epiphany moment. I almost fell out of my chair. I thought ‘it is so obvious that a book like that needs to be done’. There is plenty of fire under me to do something like that. It’s very motivating to me and I think for you as well. We share this passion for this kind of subject.”

In his book, which I thoroughly recommend, he writes about Gordon M. Burghardt and his colleagues discovering how some white-spotted cichlids were playing with a submersible thermometer.  He also writes about a banded cichlid who use to play with some cats in the home of a former animal shelter worker in Virginia. He writes about the different personalities of some garibaldis he once encountered and the distinctive personality of a reef shark named Grandma who befriended the ocean explorer Cristina Zenato. Fishes can indeed be your friends — if you let them be. 

There are many reasons why vegans do not eat fishes. For example, animal rights vegans would have ethical concerns due to fishes being sentient beings capable of feeling pain and suffering; eco-vegans would have environmental concerns regarding overfishing and unsustainable fishing practices that harm marine ecosystems and biodiversity (about 2.8 trillion fishes are killed every year by people); health vegans would have health concerns because many fishes often contain high levels of toxic contaminants such as mercury and PCBs that can be harmful to human health (the interview of entrepreneur Tony Robins in the documentary “Eating Our Way to Extinction” is particularly insightful, as he shared his experience of suffering from mercury poisoning because of deciding to become a pescatarian after having been vegan for 12 years); spiritual vegans would have philosophical and religious concerns regarding fishes having souls, being humans reincarnated, being an important part of a balanced Universe we should not mess with, or have a close kindship with us (remember that we evolved from some Sarcopterygii); social justice vegans would have socio-political concerns regarding labour practices in the fishing industry, resource depletion, and food justice. 

Whichever type of vegan you are, you will find plenty of reasons to never consider if you should abandon veganism to start eating fish, as there are many reasons not to eat them and not a valid one to do so. If you are thinking of having the recommended long-chain Omega-3 fatty acids (EPA and DHA) in your diet is a good reason to eat some fishes, you are mistaken, as fishes get Omega-3s by eating microalgae, so you can eat the algae directly to get them, or eat supplements made from algae conveniently packed for you by the many vegan companies that already exist for your convenience (and you can get the same amount of Omega-3 for less money). There is no excuse for choosing to be a pescatarian instead of a vegan — only ignorance, which you should no longer be able to claim if you read this far.

Vegans don’t eat fishes, they don’t take them out of the water with hooks for sport, and they don’t keep them captive in tanks, but nobody else should do any of that either. Humans’ relationship with fishes should be based on respect as fellow sentient beings and friendship as the interesting animals they are, not on appetite as if they were food, contempt as if they were just sport targets, or aesthetics as if they were a piece of furniture. 

It may be difficult to convince a hungry white shark being chased by a fisherperson or an aquarium kidnapper that this should be the case, but it should not be that difficult to convince a pescatarian.

You can live a fulfilled life and aim to not harm anyone. 

the photo at the end of this article is a capture of the video I took (c)CAPS and Jordi Casamitjana (1)
“Originally from Catalonia, but resident in the UK for several decades, Jordi is a vegan zoologist and author, who has been involved in different aspects of animal protection for many years. In addition to scientific research, he has worked mostly as an undercover investigator, animal welfare consultant, and animal protection campaigner. He has been an ethical vegan since 2002, and in 2020 he secured the legal protection of all ethical vegans in Great Britain from discrimination in a landmark employment tribunal case that was discussed all over the world. He is also the author of the book, ‘Ethical Vegan: a personal and political journey to change the world’.