The science of sustainable seafood, explained

Do Fish Feel Pain? Sylvia Earle talks Fishing Ethics

Syliva Earle is in the news again with a lengthy feature in Outside Magazine. Like the Newsweek article that CFood covered some weeks ago, the narrative of the Outside piece follows an interview with her lamenting the current and future state of the ocean. According to the author, Ian Frazier, the first statement Earle makes is, “The oceans are dying.” Frazier then gives a brief breakdown of ocean pollution, ocean acidification and climate change before giving way to Earle and her second major statement: “We have to stop killing fish.” The evidence Frazier gives includes “Populations of larger predators like cod, marlin, halibut, and sharks are at less than 10 percent of their numbers from 70 years ago.” Earle compares eating fish to “eating the last Bengal tigers.”

Earle is trying to humanize fish and admonish those that harm them. In one anecdote, she sees a school of anchovy in an aquarium and says: “This is not the way to see these animals. This makes them look like a mass. They are not only that—not just some endlessly abundant school. Each one of these fish is also its own individual being.”

Frazier also tells this story:

I had made the mistake of telling her that I liked to fish, and she kept asking me why. I said I just loved it because it’s my bliss and I want to follow my bliss. That argument had no effect. “But why do you enjoy torturing wildlife? It’s just a choice for you. It’s life or death for them. Why not just observe them without torturing them?” I mumbled an answer about the thrill of the chase. [Later] …since I met Sylvia, I have eaten almost no fish. The sight of sushi now embarrasses me. It is likely that big fish like swordfish, tuna, cod, and grouper will soon disappear from the sea, or from our diets, or both. We might as well completely stop eating those fish now.

Earle’s solution involves increasing the number of marine reserves, places where no human use would be allowed. Currently, marine protected areas cover about 2% of the ocean. Earle would like to increase that to 20% by 2020.

To read the rest of Outside Magazine’s feature on Sylvia Earle, click here.

Comment by Robert Arlinghaus, Humboldt-Universität zu Berlin @RArlinghausFish

I am passionate. I must be – I am a scientist. And I admire people who are passionate. I thus admire Dr. Sylvia Earle for her passionate work in relation to saving the oceans. However, as a scientist I am also an advocate of unbiased scientific facts. I thus feel unease whenever facts are inappropriately represented or biased information misused for bold claims how the world should be and how others should behave. In a recent lengthy feature in Outside Magazine the author, Ian Frazier, reports on the life achievements of Sylvia Earle. Therein one can find the following passage:

“You know that the misconception that fish can’t feel pain has been completely disproven, don’t you?” she [Sylvia Earle] asked. I said yes, I had seen studies in which fish jaws were injected with bee venom and the fish showed pain. I said I knew hooks hurt, having sometimes hooked myself.

This and some other verbiage in the article is used to showcase how terrible fishing is because it induces suffering in the world of fishes that show individuality and personality. We have a case of practical animal liberation or even animal rights philosophy at play where the suffering in the world of fishes is traded-off against the benefits of fishing to humans. Animal liberation and animal rights both are deeply anti-fishing. Usually humans tend to lose the moral balancing act because fishing is perceived by some, including Earle, as unnecessary cruelty.

That would not be a problem, per se. However, all statements in the above quotation are factually contested at best, and wrong at worst. First, fish are not known for sure to be able to feel pain or to suffer despite repeated claims for the opposite. Second, all reactions by rainbow trout in the famous “bee venom” study alluded to by Frazier are fully compatible with simple nociception, which is not pain. Third, there is also no evidence that hooks hurt fishes other than the physical damage they induce; in fact, there is strong evidence that Atlantic cod do not show any reactions at all, neither physiological nor behavioural, when hooked by a fishing hook in the lip without an associated pull on a line. They are thus unlikely to be in pain, or they show pain different to us humans. Both issues are problematic and cast doubts onto the interpretation of published behavioural experiments supposed to provide evidence for pain in fishes. In short: inferring pain from fish behaviours or from higher order cognitive concepts such as “intelligence” or “personality” is impossible because pain lacks construct ability, i.e., there is no possibility to infer pain from physiological and behavioural measures in fishes.

However, there is a simple argument that fish are unlikely to feel pain in a human or mammalian sense. When one pulls on a hook embedded in a lip of a fish, the fish, e.g., the cod in the experiment above, would fight in opposite directions to the pulling strength. This is what anglers call a fight. Imagine you would pull on a bull ring attached through the nose of kettle. The kettle would tamely follow the pulling strength, to avoid pain, the exact opposite what fishes do. Didn’t I just say we should not infer anything about the emotional life of fishes from plain behavioural data because we are humans, not fishes? Indeed. But let’s for the sake of argument anthropomorphizes how a fish might feel when hooked by a fishing hook, as Frazier does. When taken this stance, one would need to conclude from the above that fish apparently do everything (swim in opposite direction to pulling strength) to feel “pain” when hooked. One could thus conclude that fish are not only feeling “pain,” but they are likely masochistic creatures because they induce this pain on purpose. It is unlikely that any living creature would do this if they indeed would feel something that we humans call pain when hooked by a fishing hook.

One of the biggest misconception even among scientists and something that easily happens if one only superficially screens headlines of the “fish-feel-pain literature” is the confusion among nociception and pain. Most research claiming to have found (indirect) evidence for fish pain instead shows the ability of bony fishes for nociception. That fact is undisputed. Similarly undisputed are the basic neurological structures and systems that mediate pain in humans. These include two types of injury-detecting receptors (so-called A-delta and C fiber receptors); neural pathways from peripheral nerves that “talk to the outside world” and transmit information through the spinal cord and brainstem; and, ultimately, specialized regions of the cortex where the signals are processed into an emotional state that we call pain. Pain is bound to be a conscious experience and has to be mentally constructed, while nociception occurs unconsciously. Fishes can learn from nociception alone, there is no need for pain to be involved in avoidance reactions. Interestingly, fishes lack key components of the consciousness-mediating neurological systems and have no plausible and known substitute brain structures. The few fishes that have been studied have A-delta fiber nociceptors, which in humans signal localized noxious stimuli, but all studied fishes so far have very few C fiber nociceptors, which are extremely abundant in humans and in concert with the cortex (“grey matter”) that is not present in fish evoke sustained, excruciating pain. Elasmobranchs (sharks and rays) lack all types of nociceptors, yet their behavioral reactions to fishing are similar to those of bony fishes. These facts make the prospect that fishes could experience pain in a human or mammalian sense highly improbable. Indeed, when one injects capsaicin, which is a known to cause deep pain in humans and is an accepted irritant used in human pain studies, into the lip of Atlantic cod the fishes show no reactions at all. It is unlikely that Atlantic cod is the only fish on earth with a low sensitivity to potentially noxious stimuli.

Sylvia Earle’s statement related to the apparent certainty of fish feeling pain is problematic for an additional, fallacious reason – it reverses the burden of proof that fish do not feel pain. The reversed burden of proof in fact has also reversed the scientific null hypothesis from “fish do not feel pain” to “fish feel pain.” While the former hypothesis is amenable to the key principle of scientific reasoning – falsification (e.g., by finding one individual fish of any species that feels pain) – the latter hypothesis could not be falsified even if all fish of about 32,000 fish species on earth were in fact unable to feel pain. The issue is not only about semantics, but is shaking the foundation of scientific reasoning with a mission impossible. To outline the central point: imagine trying to falsify the null hypothesis “fish feel pain.” To falsify it we would need to survey all individual fish of all species on earth for their ability to feel pain. Practically aside, imagine that fish pain does in reality not exist. Under this condition we would fail to find evidence for it, even after the full census of all fishes that currently live on earth. In that case, we would maintain the null hypothesis “fish feel pain” in light of the lack of evidence to falsify it. This conclusion, however, would be wrong because in our thought experiment the fishes are not able to feel pain. By contrast, if one would start with the appropriate null hypothesis “fish do not feel pain,” lack of evidence for fish pain provide support the hypothesis that “fish do not feel pain,” which we would accept commensurate with reality. For this fundamental issue of scientific reasoning, the benefit of the doubt, with the associated reversal of the fish pain hypothesis, is scientifically untenable, albeit of stark rhetoric strength for those that happen to dislike the use of fishes on moral grounds.

Discussions on weighting fish welfare and human welfare are not new and can be traced back to the late 19th century. Scientists are passionate and hence it is no wonder that discussions related to fish pain quickly heat up, even among scientists. But these discussions should reflect the current state of affairs and not selectively quote beliefs that serve the sole purpose of fueling an underlying subjective moral argument. Therefore, based on the current state of knowledge I would rephrase the critical phrase in Frazier’s article as follows.

There is a misconception that fish are able to feel pain and that this ability has been unequivocally proved. I have seen studies in which fish jaws were injected with bee venom, but the results only support the rainbow trout’s ability for nociception, which is not pain. I know hooks hurt humans, but I have no clue what a fish feels when a hook penetrates its lips. What I know, however, is that a hooked fish behaves surprisingly different to what a mammal or human would do in similar situations.

Robert Arlinghaus is a professor at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries and the Division of Integrative Fisheries Management at Humboldt-Universität zu Berlin. You can find him on twitter here.



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5 Responses

  1. Good article but this line is weird reasoning to me- “When taken this stance, one would need to conclude from the above that fish apparently do everything (swim in opposite direction to pulling strength) to feel “pain” when hooked. One could thus conclude that fish are not only feeling “pain,” but they are likely masochistic creatures because they induce this pain on purpose”.

    1. Bill – I think it makes sense. In the thought experiment described, a mammal in pain tries everything it can to minimize pain (e.g. the bull being pulled by the ring in its nose will move in the direction of the pull – otherwise, if it resists, the ring will stretch out the flesh and cause more pain, potentially ripping through the nostril as well). Whereas fish seem to do the opposite. They get a hook in their mouth and try to fight it by moving in the opposite direction. If they felt pain the same way mammals do, we would not expect them to resist the pull of a hook through their lip, but rather move with the pull in an attempt to minimize the pain. Hope that clarifies the reasoning for you!

  2. If a bull is in enough pain they will rip out the nose ring in their panic to get away. Especially one that has never been led by the nose before. Strange example to use.

  3. Arlinghaus argues from a decidedly anthropocentric position for an industry that makes an awful lot of money from people who are content to delude themselves that because fish aren’t humans we can do to them whatever we please, a stance even easier to take if some well spoken scientist says it’s ok. It seems a little bit like a climate change scientist being paid by a coal mining company. Earle on the other hand argues (for no profit) for a sustainable ecosystem that may be able to carry the heavy burden of 7.4 billion humans some time into the future. I know who I would rather listen to.

    1. That isn’t an argument. You’re still not considering the scientific papers they’ve referenced in the article. They aren’t saying that since fish aren’t humans and therefore they can “do whatever they please”, they are using scientific research to prove the point that fish cannot feel pain. You are also falling for the oh-so-common trap of “if an industry attempts to defend itself, it’s automatically fraud by default”. If a company is using valid scientific studies to defend themselves, then they should not be written off simply because they are a company. We must consider the validity of their claims. And in this situation, science is on their side.

      “It seems a little bit like a climate change scientist being paid by a coal mining company.”

      Ironically, some of the scientists and politicians who are lobbying for “urgent action on climate change” actually are taking money from fossil fuel companies (not all of them, of course, but they do exist). Actually the AGU meeting this year was sponsored by ExxonMobil AND Chevron. But, I digress. I still do not see how this is a valid analogy.

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