The ethical case for eating oysters and mussels

It was five years ago this month that I became vegan, or…well, ostrovegan. In this blog I oystersofficially come out of the closet, err, shell.  I am almost sure that cultivated mussels and oysters are ethical to eat. I argue eating these animals is completely consistent with the spirit if not the letter of ethical veganism and the tenet of causing less harm with our consumer choices 1. This blog is on bivalve sentience/ability to suffer; for further arguments, including nutrition arguments, see my second blog.

Are mussels and oysters sentient?

Dividing organisms up into types, or cladistics, is tricky business. Nature did not develop in a way that fits neatly into categories. Dividing up organisms on the basis of sentience, or the ability to suffer, may be even trickier. So, is there any evidence that mussels and oysters don’t suffer?

Argument 1- Oysters and Mussels are not motile

Let me start with a perspective derived from evolutionary theory about how organisms are designed. The function of pain is to help an organism avoid stimuli that may cause them bodily harm. Organisms that are sessile, or unable to move, cannot escape pain and thus there really isn’t any adaptive reason for them to feel pain. Sessile bivalves can open and close their shells but this is as simple an action as plants who close in the presence of noxious stimuli and for a variety of reasons I won’t go into here, plants don’t feel pain. The definition of vegan typically includes not consuming anything of animal origin. And, as animals are most often motile and thus have an adaptive reason to feel pain, this makes sense.

But, mussels and oysters are closely related to other species (e.g. scallops2, squid) who are motile and thus, by my logic, can feel pain, is it possible that they have some leftover capacity to suffer from a common ancestor?3

This is very unlikely because pain is biologically expensive4 In order to feel pain an organism must have to have a sensory system capable of differentiating ‘good’ or adaptive stimuli from ‘bad’ or harmful stimuli. On top of this, the experience of pain is often damaging in and of itself. Finally, in order to facilitate moving away from pain an organism’s priorities change. For instance, pain reduces hunger and the desire to mate. Given that no system is perfect and there is always some rate of misfiring, a sessile organism that experiences pain would get all the harm and none of the benefit of moving away from painful stimuli and thus be at a disadvantage.

-Oysters and mussels have a larval stage that is motile (see this and this). During this larval stage the animals react to stimuli and may even hitch a ride on fish to disperse more widely.  Also, freshwater mussels (which are not commonly eaten by humans) are more motile and can move (albeit slowly). During the larval stage there are neurons present however “many of the larval neurons disappear after metamorphosis“. Both of these facts make me less confident in the motility argument but I still think the other arguments below stand on their own. /Addendum

Argument 2- Oysters and mussels have rudimentary nervous systems and do not seem to use endogenous opiates or opiate receptors to inhibit pain

Mussel nervous system

“[The bivalve] nervous system includes two pairs of nerve cords and three pairs of ganglia. There is no obvious cephalization and the nervous system appears quite simple….to our knowledge there are no published descriptions of  behavioral or neurophysiological responses to tissue injury in bivalves (Crook& Walters 2011).


Translation: Bivalves have a very simple nervous system which is not aggregated in anything like a brain. Other invertebrates, like shrimp, show changes in behavior (e.g. grooming their antenna after injury) neurotransmitters or neural firing in response to injury, but previous studies have not shown this kind of response in bivalves.

My conclusion: Bivalves do not have hardware or response consistent with the ability to feel pain. Because they have no brain, or central processing unit for stimuli, there is no ‘there’, there. Just like a disembodied finger, there is no place for sensations to be aggregated into responses or changes in adaptive decision making.5

Many animals have opiate receptors, indicating they are making painkillers and regulating pain within their own nervous system. One way that animal pain is gauged is to administer opiates and see if it influences the behavioral response to pain (e.g.). There is some evidence that bivalves have opioids and opioid receptors but 1) there isn’t good evidence that bivalves have the genes that code for these receptors and 2) it seems that opiates are being used to signal the immune system not to regulate pain. To be honest this is the point on which I am least confident and on which science isn’t yet conclusive.

Argument 3- Eating cultivated oysters and mussels doesn’t doesn’t kill other (sentient) animals at a rate greater than agriculture

Line grown mussels

No food is completely deathless. When you eat plants or grains you are often supporting a  system that kills insects, rodents, and displaces wild animals. Let’s say that you eat shrimps because you doubt that they are sentient. Even if you are on an invertebrate only diet, many species are dredged or netted which involves bycatch, or the deaths of many other organisms after they are harmed by being brought up out of the water and thrown in again. With shrimp, for instance, the rate of bycatch is enormous, sometimes up to 98% of what is caught is discarded, and much of this bycatch is vertebrates. Surely, eating animals that aren’t sentient could not be ethical if it involved significant numbers of deaths for animals that are sentient.

Mussels and oysters, on the other hand are most often farmed in a way that doesn’t involve harm to other sentient beings. From what I can tell from reading in depth about cultivation:

-The only dredging involved in cultivation is collecting spat, or the “seeds” that become mature mussels, however rope cultured mussels don’t generally involve dredging for spat but collecting it on the surface thus not displacing other organisms.

-Oyster and mussel cultivation has been endorsed as good for water quality (e.g. they filter out excess nitrogen) doesn’t involve antibiotics and doesn’t involve killing other animals to feed to them as is the case with farmed fish (e.g. this source is not objective but details many potential environmental benefits from shellfish aquaculture).

-Eating oysters and mussels may involve less other animal death and displacement than eating grains or soy (although I have yet to do a proper calculation on this)

In the next blog I’ve argued that including oysters and mussels as ethically acceptable on a vegan diet undermines naturalistic, nutritional and emotional arguments against veganism thus promoting ethical eating. I’ll also speculate about whether there would be fewer vertebrate eating ex-vegans if ostrovegan was considered an ethically acceptable in a vegan diet. 


1-I’m not the first to argue this. This Slate piece from back in 2010 sketches the argument from sentience and Peter Singer has also been on both sides of this argument earlier endorsing and later renouncing the view that eating sessile bivalves is ethically neutral.

2-I endorse giving motile bivalves like clams and scallops the benefit of the doubt and not eating them. Scallops can swim away from predators and have eyes, which makes them a great deal more cognitively sophisticated.

3-Hat tip to Ian McDonald for pointing out this possibility

4– Brains, often needed in motile organisms, are also biologically expensive:

“The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task, it has a rudimentary nervous system. When it finds its spot and takes root, it doesn’t need its brain anymore, so it eats it! It’s rather like getting tenure.” – Daniel C. Dennett

5David Pearce, who disagrees with me and thinks that we should give oysters and mussels the benefit of the doubt (partly because of possible opiate receptors) has conceded this:

“Just as I think it’s possible some of our peripheral ganglia feel phenomenal pain that is inaccessible to the CNS (cf. how one sometimes withdraws one’s hand from a hot stove before one feels the searing pain) it’s possible mussels and oyster ganglia feel something similar. But rights for individal nerve ganglia clearly can’t be high on our list of moral priorities”

120 thoughts on “The ethical case for eating oysters and mussels

  1. All irrelevant. What matters, is the oyster life. Life is important, as my life is important to me, so is the oysters life. Do we NEED to eat oysters to live? No we don’t. Therefore, it’s imoral to eat them. We can choose not to end their lifes. If it’s not necessary, we shouldn’t be killing and eating them. If we choose to “make an exception” on oysters, then we are being speciesists, considering that our moment of pleasure on one meal, is morally more important then an oysters life. It’s not. Life is always more important then satisfying our palate. And yes. Animal life IS more important then plant life. Animal life it’s complex life. You can kill an animal, like an oyster. You can’t kill a carrot or an apple. Animal life and Plant life are completely different things. And you know it.

    • In my case, while I don’t necessarily have to eat oysets or mussels (and generally don’t) I do have to eat meat. I am biologically adapted to eating meat (internal organ differences) and physically lack the ability to fully digest vegetable protein. My tribe lived exclusively on meat and fish for thousands of years which helps explain the selection pressure against vegetables. (Well, technically, even a Panda – which biologically adapted to eating meat – can choose to live only on vegetables. The problem is that I would have ti eat vegetables almost constantly and even then there is no guarantee I could eat enough)

      As far as plants not being alive? They are alive and they are capable of feeling pain. Maybe not as neurons, but they have the ability to experience and respond to stimuli. A carrot is alive, but an apple is not. Or rather, not alive in the sense that it is harmed by eating it.

      My argument is that since both plants and animals are alive it’s wrong to kill anything (not just animals), but since we must eat to live it is forgivable to kill when we must.

      In my area most Kale growers kill the plants each harvest and replant, but that’s not necessary. It’s morally wrong. I take care of them through multiple years harvesting from just the leaves and picking only at leaves that are blocking light to other leaves. In this way I can harvest without harm. When winter comes along I create a warm space for plants to come inside taking at least cuttings so that part of the whole can survive. I do this because I value their lives. I feel responsible for them. in return they provide me with vegetables that help to balance the meat I must consume.

      While many people can indeed live on vegetables only it’s important to consider the impact there as well. For example, if you buy your vegetables from a farm with chemical run offs into rivers those chemicals will feed to the ocean and ultimately kill animals. If eating vegetables results in the death of animals your salad is no different morally than a tuna sandwich. Of courde, if you grow most of your vegetables like I do, or get it from local sources that don’t use such methods you can side step that issue. But what about synthetics? If that synthetic coat pollutes an area and leads to dead animals how is that morally different from buying leather? I would argue that it is far better to use animals – the whole animal – than it is to harm the environment. Again though, not all synthetics have that problem, but if you don’t care enough to look that’s where it’s coming from its immoral overall.

      All life is sacred. Everything is connected. We are part of the whole, not separate from it.

    • May I ask, what is it that differentiates the life of an insentient oyster and a plant? You can definitely “kill” a carrot or an apple. First of all the concept of “killing” is manmade and is basically the “purposeful ending of a life”. So what is your definition of life? What makes a clam more alive than a plant? The fact that it moves? Well, so can a venus fly trap. I feel that most people would argue that plants are very much alive.

      However, I continue to eat plants because they are not sentient beings that suffer, and with that logic, eating clams/oysters would be completely valid.

      I, myself, don’t eat clams or oysters- but I really can’t find a logical explanation as to why a vegan shouldn’t. Your argument reflects spirituality more than scientific evidence- which just doesn’t really speak to me.

    • “All irrelevant. What matters, is the oyster life.”

      If the creature is sessile, feels no pain and can be grown and harvested ethically it is no different than consuming a plant. You are hugely over complicating the issue.

      Do you NEED the laptop/computer/phone you wrote your reply on to live? No? Than the pollution created smelting the elements to create your device makes using it immoral.

      Do you NEED to eat apples to live? etc etc etc etc

      I haven’t eaten any animal since changing to a plant based diet but until someone can make an argument deeper than “Do we NEED them to live?” as a reason to not eat something which feels no pain, has no brain and doesn’t move I can see no reason why there is anything wrong with eating them. Sure, it’s not “vegan” in that it’s an animal protein but I’d rather choose to try and live my life ethically rather than what fits into the confines of a label.

    • All inaccurate comment.

      Yes, my life is important to me, but not because i’m alive : because i’m AWARE of being alive. Because I am SENTIENT. If you are not sentient, how in the world could your life be important TO you ? So opinions aside, from the moment we agree on oysters being sentient, your sentence about oysters’ lives being important to them is false.

      My opinion is that life has not such importance compared to sentience. My definition of veganism would be about not give pain to sentient beings and not kill sentient beings (’cause by killing them, even without pain, you prevent them to enjoy the future of their lives). My definition of veganism would not include the words “exploitation” or “animals”. I mean, if a vegetable is sentient, I will not eat it. And if an animal is not sentient, I don’t see a reason why not eating it.

      You accuse me of being SPECIST because I say that I could eat oysters but not pigs for instance. But if I say such a thing, it is not because of their different species, it is because ones are sentient and the others are not. If you don’t get my point, think about it this way : compare an INDIVIDUAL pig and an INDIVIDUAL oyster. I know that the first is sentient, and the other is not, so I eat the second. I don’t give a shit about the species… Maybe we had to think in terms of species to eventually conclude that all individuals of a particular specie is sentient or not, true, but that doesn’t make me a specist.

      And now the most ridiculous thing : after calling me a specist, you end up saying that animal life IS more important than plant life, because we can kill animals but not plants. Are you serious ? You pretend to be a “life” worshiper and you don’t even know that plants are alive too, which means it is possible to kill them ?
      Of course, as you say, plants are less complex than animals, yes, and the very first consequence/cause of this is that they are not SENTIENT. But oysters are neither sentient. You are the one being specist if you stupidly follow distinctions made by human beings with no real reason (animal vs plants). Use your brain.

    • You’re being completely anthropocentristic and ridiculous. Biology doesn’t work “in boxes” and the difference between animals and plants in nature isn’t as clear as you think. Of course you CAN kill a carrot, you can hurt the plant, you can exploit the plant, etc.

    • I’m just trying to understand other thought processes. I just ate steak so I’m not arguing for one side or another. Just an honest question. Your argument of a carrot or Apple made sense to me but what about plant life where what you are eating is the plant and kills the plant. Like Heart of Palm for instance. Is that unethical to a vegan?

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  3. The comments on this blog are extremely intelligent and thought provoking. Im finding it hard to make the decision on whether eating clams etc is ethical. Some of the comments on here have also really opened my eyes and developed my understanding to other issues. Its really hard to make the right choices sometimes we all need to just keep trying our best I suppose.

  4. Wonderful discussion. Thank you everyone. In my mind, sentient means something that knows it’s alive. That’s from a Buddhist perspective, and I mean the science behind Buddhism, not the religion so many people have made it into. The generally accepted definition of Buddha is someone that has awakened to reality (truth, whatever). I think we can stretch that a bit. Our companion cat lives a life of no harm, except for the occasional lizard that she catches. She certainly understands cause and effect, and she’s smarter anda better “person” than 99% of the people I have met, so I would say she is “awakened”. Would someone, no matter what the species, harm another being if they knew it would cause them death?

    I know from my own experiments that I carried out decades ago after reading “The Secret Life of Plants” that plants appear to feel empathy w/ the suffering of other plants. but I would argue that these reactions are essentially just that, reactions. Just like a dead frog, which is certainly not alive, can be made to move by hitting it w/ electricity. Does a plant have a nervous system and a brain? No, so eat ’em up! We do have to eat something to live. I myself like living. It’s the bomb, and beats the alternative. Give me a terminal disease and put me in dire suffering and I may feel differently, but until then I plan on dancing for as long as I can.

    Then there’s the slippery slope of more, and less, sentient beings. Quite a moral trap, but if someone, maybe for medical reasons ,has to eat dead living beings, then it’s smarter to choose the less sentient ones. Shrimp may indeed repair their antenna, but plants do repair and regrowth jobs on themselves too. Does a bivalve? I don’t know.. Does it have what we would call a brain and a central nervous system? No. Does it know it’s alive? No. Does it feel pain? I’m not up on my biology, so I don’t know? Is it a living being? Ah, that’s one for thought. Do we HAVE to eat them to live? That’s the issue to me? Well, I personally don’t. Would I eat them if I were offered them in a meal prepared by someone else? I’m not sure anymore, and this article has me thinking about my definitions of life. Thank goodness I can lead an ethical food life even in a fast food restaurant by choosing things like orange juice, french fries, and a salad. Some places offer a little more than that, but those will do me fine for an occasional outing. I’m not going to torture myself about whether or not chemical run offs killed or displaced other beings though. That’s too far. From that perspective you could argue that killing ANYTHING destroys living cells. so there would be nothing under the sun to eat but rocks and minerals and the like. Thanks again for putting this article, and the comments are excellent.

  5. I have been vegan for over a year. Recently I started wondering about oysters, mussels etc (although I don’t actually and have never really like mussels), you know the whole theory about “don’t eat anything that can run, jump, swim, hop or walk away from you if it has to”? So I feel, that if an oyster can’t do any of that (and as I now found out scallops can so that is off the list), and I take all the ethical and environmental points in from above as well as the health benefit of B12, then why not? But I still don’t know if I would, and I think that in itself tells me my answer, if I have to wonder, and I don’t need them to live, then why should / would I? So I don’t know, maybe one day I will make a decision to order a plate, but again even after all this research, not sure if I want to? Too many “what if’s” for me…

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