Swimmingly forward: Fish welfare, pain and intelligence

By Holly Molinaro & Sabrina Brando

Usually, we release one Science into Practice (SiP) resource every week. For this month, we have a little bonus for you. Two SiPs in one week! You can access all materials via the PAWS platform, not a member yet? Become one HERE or sign up for more blogs like this via our newsletter!

This week, both SiPs are about fish welfare, pain and intelligence.

One of the reasons for this is that we would like to discuss and cover a wide variety of topics and stances, including the ones we do not necessarily adhere to. We should make all efforts to not fall into the trap of excluding information just because it does not fit our worldview, philosophy, or opinion, but rather discuss openly and put forward our ideas, thoughts and feelings, bringing in all the science and other perspectives available to have a deeper conversation.

(1) Rose (2007), Anthropomorphism and ‘mental welfare’ of fishes


(2) Sneddon (2019), Evolution of nociception and pain: evidence from fish models

However, both offer a different viewpoint of where fishes really land on these abilities. Don’t forget we are talking about over 34.000 species according to FishBase, so it is hard to say something about all species to start with and we have to start somewhere.

PAWS is all about practical resources rooted in science (as well as ethics and humanities, but that is for another blog). Therefore, it is important to fully understand different sides of an animal welfare issue to the best of our abilities in order to gain better clarity surrounding a potentially controversial topic. One of these topics is pain in fishes.

Before you read further, what are your beliefs of pain in fish, can they feel pain? Do they emotionally suffer from physical pain, can they suffer from emotional pain? It important to connect to our thoughts, our believes, and while we want to make an evidence-based decision (and what is considered evidence is for another blog), it is also important to think through and muse on the 'what ifs, reflected in how we show up for animals from an 'over-attribution perspective, a 'the burden of proof is on us' approach and consideration and respect for others who we do not understand fully, what their lived and felt experiences are like. There is so much more to say about this but that is for another time as well, let's go with the fishes for now!

First of all, we would like to make it clear that we do not share the opinion coming from the first SiP, Rose (2007), Anthropomorphism and ‘mental welfare’ of fishes. With new research emerging (as we will detail below), the argument that fish do not have the ability to feel pain is outdated. However, that is still a viewpoint many people, also in the animal care and welfare field, do agree with and therefore, important to continue to discuss. I, Sabrina Brando, attended a fish welfare meeting in 2010 with prominent fish researchers such as the late fish biologist and professor of fisheries and biology at Penn State University Victoria Braithwaite who found extensive evidence that fish are capable of conscious pain and should be granted similar protections as birds and mammals. Learn more about her book ‘Do fish feel pain?” (2010) here. And as you can see the discussion is ongoing.

Rose (2007) argues that anthropomorphism has gotten in the way of truly understanding fish cognitive abilities. To refresh, anthropomorphism is the tendency for us as humans to attribute human-like characters to non-human organisms or things. Rose (2007) states that humans have just assumed the ability to feel pain in fish simply because humans also feel pain. However, Sneddon (2019) creates an argument without the influence of human presence at all. Sneddon writes “there is ample evidence to demonstrate that it is highly likely that fish experience pain”. Through her review article, she details an amplitude of research that details the pain experiences fish can feel.

So, let’s take a dive into just some of the research on fish sentience, intelligence and pain.

Sentience is described in various ways - it seems coined by philosophers in the 17th century - "capable of feeling," from Latin sentientem, revolving around the capacity to be aware of feelings and sensations as distinguished from perception and thought. Follow this link to learn more about the different approaches and ideas on what sentience is, there are several papers describing the continued debate on this topic, but that will have to be for another blog. 

While the term ‘fish’ constitutes a large array of different species, evidence from one species can give rise to a better understanding of the entire taxa. For instance, Balcombe (2016) demonstrates thinking and feeling abilities in Tigerfish (Hydrocynus vittatus) through their ability to ‘swallow feed’ aka leap out of the water and eat a barn swallow. Through behavioural observations, it can be noted that birds are not usually on the tigerfish’s menu, however, there are cases when this fish hunts opportunistically and with some type of plan. For a different species, the Rabbitfish (f. Siganidae) Brandl & Bellwood (2015) documents this fish foraging in pairs, showing cooperation and reciprocity. Motivation in tilapia (Oreochromis mossambicus) was shown in Galhardo et al. (2011).

Soares et al. (2011) show how physical stimulation in surgeonfish (Ctenochaetus striatus) lowers stress, a process as of before only known in humans. da Silva et al. (2018) documented how behaviour in response to a noxious stimulus has been affected by anxiety, fear, or stress in zebrafish (Danio rerio).  Vail et al. (2013) provide evidence of collaborative hunting between coral reef fishes (grouper Plectropomus pessuliferus marisrubri) and coral trout (Plectropomus leopardus) and giant moray eels (Gymnothorax javanicus). The process of collaborative hunting has only been seen in humans, great apes and ravens. And Heathcote et al. (2017) used social network analysis to showcase guppies (Poecilia reticulata) form stronger social bonds when under predation. Altogether, these examples showcase that the preconceived notions of fish without any sentient abilities are just simply not true. They demonstrate fish have an awareness of themselves as well as others.

Both articles discuss the biological and physiological mechanism of pain. Pain can be perceived through nociceptors, which are nerve cells that pick up on potentially dangerous or harmful stimuli. Rose and Sneddon both agree that this nociception is the start of the process of feeling pain. In addition, they also agree that for the stimuli to truly be felt as ‘painful’, the organism must have some sort of conscious process which registers it as harmful and tries to avoid it in the future. However, Rose argues that fish probably do not have this conscious ability while Sneddon says that they probably do.

Rose’s article was published in 2007, while Sneddon’s was published in 2019. Does this mean simply there was not enough research at the time to conclude fish have the ability to feel pain and now that we know more, we can accept it? Unfortunately, no. In 2016, a controversial article was written regarding the lack of ability for fish to feel pain (see Key, 2016). Almost 10 years after Rose’s article, this stance is still promoted by multiple researchers.

While having the ability to feel pain is one thing, cognitive abilities in fish are another. Renowned research Victoria Braithwaite (mentioned above) has written several articles about the ability for fish to feel pain and suffer, but also to learn and positively interact with environmental enrichment. Braithwaite & Huntingford (2004)’s work details that fish do feel pain and therefore can suffer. In addition, Odling-Smee & Braithwaite (2003) document that fish use learning and memory to orient themselves in their environments and as well use landmarks for direction and understand complex spatial relationships. Fish can also learn in relation to their foraging habits and abilities, recognize their conspecific, learn from a social-environmental perspective as well as demonstrate spatial learning (Braithwaite, 2006)Finally, Salvanes et al. (2013) showcase the effects of environmental enrichment in promoting neural plasticity in Atlantic salmon (Salmo salar). Fish exposed to enrichment displayed improved learning ability in a specific spatial task.

Sneddon et al. (2018) document several examples of fish sentience and pain. Of note, it has been found that anaesthetics have a similar effect in plants as they do in fish, however in fish they act on brain receptors (Yokawa & Baluška, 2018). Fish have also been readily used in biomedical research regarding pain, which in itself implies there is consensus that fish feel pain (Martin & Gerlai, 2018) and Demin et al. (2018) point out that zebrafish have been used as substitutes for laboratory rodents in understanding human physiology. These examples support Sneddon et al. (2018)’s case that fish probably (strikethrough added by us) do feel pain. The authors also bring up an interesting point about the way in which fish are described. The word “harvested” is often used when referring to fish as they are seen more as a commodity and resource rather than a living and breathing animal. Using terms like these can often cause bias, rather conscious or unconscious when trying to fully understand fish cognitive abilities.

While the feeling of pain has been documented in fish, this does not mean these affective experiences in fish are identical to that of humans. More research detailing exactly how fish feel pain is surely needed in the future. Sneddon & Leach (2016) argue that the “incompleteness” of fish pain and sentience research does not mean that fish cannot have these abilities, rather, just more research needs to be done - hence our note above on how we show up.

The future of fish welfare research is going swimmingly, however. A recently published article (Sánchez-Suárez et al., 2020) reviews fish welfare studies from an aquaculture perspective. While noting there is still a lot of work to be done, the authors call for a focus on understanding and increasing fishes’ positive states, as well as minimizing negative ones. Read more on ongoing work such as providing environmental enrichment to salmon raised on farms in Time to play.

Of course, we should not forget our fish friends in positive activities such as environmental enrichment, everyone needs to have seen enrichment with rays by Teambuilding with Bite, fish training by Loro Parque or shark enrichment at the Aquarium of the Pacificall wonderful efforts of facilities around the world (indirectly) caring for fishes!


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