Perhaps you read our article on animals’ capacity to experience pain. The examples in that piece focused mainly on mammals and birds, but what about fish? Is there evidence that fish can experience pain in a similar way to birds and mammals?
FISH! Are They Our Friends or Are They Food?
UNQUANTIFIABLE FISH FATALITIES
Extrapolating from data from the FAO Fisheries and Aquaculture Department, it is estimated that every year 970-2700 billion fishes are caught from the wild , and 37-120 billion are killed in fish farms . The reason these figures are extrapolated is because the official records for global fish production are measured in tonnes, not individual fish. (See the studies referenced for details of how these calculations were made).
A STRONGER AFFINITY WITH MAMMALS
Surveys have shown that fish tend to come out at the bottom of the pile when people are asked to rate the sentience of different species of animal [3, 4]. It is likely that the popularity of a pescatarian diet can be attributed to the difference in people’s attitude towards fish compared to other animals.
Although there is no definitive survey data showing the number of pescatarians, the Vegetarian Society have collated data from a number of different surveys about diet and attitudes to food on their website: The results of these surveys indicate that there are similar numbers of vegetarians (eat no meat or fish) as pescatarians, or in some cases more pescatarians than vegetarians. For example, in a 2005 FSA survey of 3,143 adults, 4% households contained at least one vegetarian member, and 5% contained at least one person who ate no meat, but did eat fish.
Another example is a 2011 Vegetarian Foods Market Assessment Report which found that 6% of people classed themselves as ‘mainly vegetarian’ (ate fish but no meat), while 3% were estimated to be completely vegetarian.
Purely anecdotally, I have met many people who ascribe a lower moral status to fish compared to other animals, and reflect this in their dietary choices, but I have yet to meet someone who avoids eating fish on moral ground, but eats birds and mammals.
LITTLE PROTECTION FOR FISH WELFARE
This lack of care for our fishy friends affects the way they are treated at slaughter. The current EU legislation protecting animals at the time of killing (European Council Regulation 1099/2009) states that “Many killing methods are painful for animals. Stunning is therefore necessary to induce a lack of consciousness and sensibility before, or at the same time as, the animals are killed”. However, fish are specifically excluded from the provisions laid out in this legislation.
The Farm Animal Welfare Committee (FAWC) released a report in 2014 detailing areas of farm animal welfare legislation that fail to cover the needs of fish, concluding that “fish are, therefore, not offered the more detailed welfare protection during production afforded to most terrestrial farm animals”. Although the FAWC report recommends stunning of fish prior to slaughter, the vast majority of fish harvested for food are killed by asphyxiation in air or on ice, mainly because this involves very little extra effort or cost .
Despite the commonness of this killing method, it is not considered humane ; one study found that seabream transferred from water to ice took approximately 5 minutes to lose normal patterns of brain activity  and a Compassion in World Farming report suggests that “(s)uffocation in air can take up to 9 minutes to result in loss of consciousness”.
Together, the staggering numbers of fish killed, lack of empathy from the public, and lack of appropriate regulations for humane killing methods paint a pretty grim picture for fish. Of course, none of this matters if fish are unable to suffer, so what does science say on the subject?
CAN FISH FEEL PAIN?
Unfortunately, as with many areas of science, there is no unanimous consensus on whether fish can suffer or experience pain in the same way as humans and other animals. Some argue that because fish lack the brain structures present in humans and other animals which are associated with pain perception (i.e. specific regions of the cerebral cortex), they are incapable of experiencing suffering and pain [7,8]. However, others argue that a lack of these specific brain structures is a weak argument for denying pain in fish, when birds also lack these structures and the scientific consensus is that birds are capable of feeling pain .
Behavioural studies have been carried out which suggest that fish can feel pain. For example, Sneddon (2003) found that when a noxious chemical was applied to the lips of trout, they displayed physiological and behavioural reactions which suggested pain; the trout were observed rubbing their lips in the gravel or on the walls of their tank, and their gill ventilation rate (equivalent of respiration rate) increased almost double fold. This same study also found that when an analgesic was administered to the fish (morphine), the incidence of pain related behaviours and gill ventilation both decreased significantly .
Another study showed that fish would avoid an area of their tank where they had previously been given an electric shock, even if they had previously learnt to associate that area with food. The amount of time the fish spent in the shock/feeding zone decreased when they were given more intense electrical shocks, and increased when they were deprived of food, which suggests that the fish were “weighing-up” the negative experience of the shock against the need for food . The debate still rages on, for a list of articles arguing both sides of the topic please see here.
It seems that science can’t currently reach a conclusion on whether fish can feel. Those in the “anti-fish feelings” camp argue that the behavioural and physiological responses observed are merely unconscious reactions to potentially damaging stimuli, and do not prove that fish subjectively experience pain and suffering. Those in the “pro-fish feelings” camp will often acknowledge that we can never 100% tell how an animal feels, since they can’t tell us, but there’s reasonable evidence to give them the benefit of the doubt.
I fall into the “benefit of the doubt” camp; because I know I don’t need to eat fish to be healthy, I don’t think it’s worth the risk of assuming they can’t feel pain and potentially contributing to suffering through my diet choices. I think the negative implications of wrongly assuming fish CANNOT feel pain are worse than the negative implications of wrongly assuming fish CAN feel pain.
What are the negative implications of wrongly assuming fish can’t feel pain, you might ask; some authors have argued that that it could “lead to legislative restrictions on fish-related activities with potentially serious negative implications for native subsistence fishing…, human nutrition and food supply…, and economic development” .
I find it interesting that this particular quote focuses on “native subsistence fishing” rather than the massive commercial fishing industry that would also certainly take a hit. I suppose it is far easier to sympathise with small-scale subsistence fishing (which conjures images of a lone, weather-beaten fisherman, paddling out into the rough seas in a leaky wooden boat, armed only with a fishing pole and a bucket, to bring back supper for his family), than the massive commercial fishing vessels trawling the seas, scooping up all marine life in their path.
 Mood, A. and Brooke, P. (2010) Estimating the Number of Fish Caught in Global Fishing Each Year. (link)
 Mood, A. and Brooke, P. (2012) Estimating the Number of Farmed Fish Killed in Global Aquaculture Each Year. (link)
 Phillips C.J., McCulloch S. (2006) Student attitudes on animal sentience and use of animals in society. J. Biol. Educ. 40: 17–24. (link)
 Phillips, C.J., Izmirli, S., Aldavood, S.J., et al (2012) Students’ attitudes to animal welfare and rights in Europe and Asia. Animal Welfare 21: 87-100. (link)
 Lines, J.A., and Spence, J. (2014) Humane harvesting and slaughter of farmed fish. Revue scientifique et technique. 33 (1): 255-264. (link)
 Van de Vis, H., Kestin, S., Robb, D., Oehlenschläger J., et al (2003) Is humane slaughter of fish possible for industry? Aquaculture Research 34: 211–220. (link)
 Rose, J.D. (2002) The Neurobehavioral Nature of Fishes and the Question of Awareness and Pain. Reviews in Fisheries Science 10(1): 1–38. (link)
 Key, B. (2016) Why fish do not feel pain. Animal Sentience 003 (link)
 Balcombe, J. (2016) Cognitive evidence of fish sentience. Animal Sentience 008 (link)
 Sneddon, L.U. (2003). The evidence for pain in fish: the use of morphine as an analgesic. Applied Animal Behaviour Science, 83(2): 153-162. (link)
 Millsop, S., Laming, P., (2008) Trade-offs between feeding and shock avoidance in goldfish (Carassius auratus). Applied Animal Behaviour Science 113 (1-3): 247-254 (link)