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

5-David 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”

About these ads

110 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.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s