The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage. The inability to communicate verbally does not negate the possibility that an individual is experiencing pain.”

It seems extraordinary that it has taken us so long to ask the question: do fish feel pain? Accepting that an animal has the ability to suffer pain changes the way we choose to interact with it. It should influence the moral and ethical judgements we make.

Victoria Braithwaite, in her book Do Fish Feel Pain, presents scientific evidence that fish are smart and cognitively competent beings. This is consistent with hundreds of studies showing that fish are intelligent and have both accurate and long-lasting memories, which in some cases, such as migrating salmon, can span years. Fish do not audibly scream when they are impaled on hooks, or grimace when the hooks are ripped from their mouths, but their behaviour offers evidence of their suffering—if we’re willing to look.

Not so different

Fish have all our senses and more. A thin lateral line runs along the flank, with special sensory receptors, which allow the fish to detect nearby objects. Blind-cave fish, living in underground caverns in Mexico, use this for ‘seeing’. The electric eel, with a specialised organ located towards the end of the tail, can generate enough electricity to stun prey. Knife-fish, or elephant-nose fish, generate weaker electric signals used for communication.

How different are fishes from humans? Conspicuous parallels emerge. Apart from the backbone, their ‘stress response’ is strikingly similar to that of mammals.

The fish brain also has a forebrain, midbrain and hindbrain. However, fish do not have a neocortex. This plays a central role in the fish pain debate—even those who argue fish cannot feel pain consider the neocortex essential for an animal to experience feelings. MRIs show us that the neocortex is not the only part of the brain that is active during painful events. Many other parts of the brain overlap and take on functions. Dr Ian Duncan reminds us that we “have to look at behaviour and physiology,” not just anatomy. “It’s possible for a brain to evolve in different ways. That’s what is happening in the fish line. It’s evolved in some other ways in other parts of the brain to receive pain.”

Fish, like ‘higher vertebrates’, have neurotransmitters, such as endorphins, that relieve suffering. Researchers have created a detailed map of pain receptors—which includes those very areas where an angler’s barbed hook penetrates. As Dr Stephanie Yue writes, “pain is an evolutionary adaptation that helps individuals survive. A trait, like pain perception, is not likely to suddenly disappear for one particular taxonomic class.”

A nociceptor is a sensory nerve cell that responds to damaging, or potentially damaging, stimuli by sending signals to the spinal cord and brain. It initiates the sensation of pain (noci is Latin for “hurt”). Nociceptors in fish are strikingly similar to those found in mammals, and they respond to heat, pressure and noxious chemicals such as acid and bee venom.

In 2004, physiologist Lynne Sneddon published a study saying that fish can detect and feel pain. Sneddon discovered 58 pain receptors, called nociceptors, along the trout’s lips resembling those in amphibians, birds and mammals including humans. She did so by injecting bee venom and acetic acid into the mouth area. The affected fish exhibited behaviour that clearly showed extreme stress, such as rubbing their noses into gravel and shaking their bodies. Fish demonstrated a ‘rocking’ motion, strikingly similar to the kind of motion seen in stressed higher vertebrates like mammals. Since morphine appeared to ease the discomfort, Sneddon concluded that the trout’s reactions weren’t simply reflexive but genuine displays of pain response. The fish injected with venom and acid also took almost three times longer to resume feeding than the control groups.

More proof

Trout are ‘neophobic’—they actively avoid new objects. But those injected with acetic acid showed no reaction to a brightly coloured Lego tower placed in their tank, suggesting that their attention was focused on the pain. In contrast, trout injected with saline—as well as those that were given painkillers following acid injection—displayed the usual degree of caution regarding the new object. Similar results have been demonstrated in human patients suffering from painful medical conditions. We all know that pain interferes with our normal thinking abilities.

Researchers at Purdue University reported that goldfish experience pain consciously. Goldfish injected with saline solution, and exposed to a painful level of heat in a test tank, ‘hovered’ in one spot when placed back in their home tank. Fearful, avoidance behaviour is rational—not involuntary. Other fish, after receiving a morphine injection, showed no such fearful behaviour.

A study by scientists, at Queen’s University Belfast, proved that fish learn to avoid pain, like other animals. “They avoid areas where they have been hurt, they will not repeat a previous action that has caused pain. This avoidance is learned, remembered and is changed according to different circumstances.”

In a 2014 report, the Farm Animal Welfare Committee (FAWC), an advisory body to the British government, stated, “fish are able to detect and respond to noxious stimuli, and FAWC supports the increasing scientific consensus that they experience pain.”

Fishing is nothing more than a cruel blood sport. When fish are impaled on an angler’s hook and yanked out of the water, it is not a game to them. They are scared, in pain, and fighting for their lives. Michael Stoskopf, professor of aquatics, wildlife, and zoologic medicine at North Carolina University, said, “it would be an unjustified error to assume that fish do not perceive pain in these situations.” Researcher Dr Culum Brown concludes that “it would be impossible for fish to survive as the cognitively and behaviourally complex animals they are without a capacity to feel pain” and “the potential amount of cruelty” that we humans inflict on fish “is mind-boggling.”

An experiment involved electrically shocking toadfish in order to observe their responses to stimuli that would be painful for humans and other mammals. It was found that the toadfish would grunt whenever they were shocked. After some time, the toadfish began to grunt at the sight of an electrode, without yet being shocked. This shows that fish exhibit pain-response and pain-association behaviour seen in us and other animals.

Miserable world

Peter Singer writes, “there is no humane slaughter requirement for wild fish caught and killed at sea, nor, in most places, for farmed fish.” Fish caught in nets by trawlers are dumped on board the ship and allowed to suffocate. Using live baits on hooks is a common commercial practice: long line fishing, for example, uses hundred or even thousands of hooks on a single line that may be 50-100 km long. When fish take the bait, they are likely to remain caught for many hours before the line is hauled in.

Likewise, commercial fishing frequently depends on gill nets—walls of fine netting in which fish become snared, often by the gills. They may suffocate in the net, because with their gills constricted, they cannot breathe. The first ever systematic estimate of the size of the yearly global capture of wild fish is about 1 trillion to 2.7 trillion, about 150 times the number of mammals and birds killed for consumption.

Can a planet survive after so much pain has been generated? There is so much violence in the air we breathe. Can we be happy if every being around us is unhappy? The miasma of viciousness hangs like a black pall over us. No wonder we are so miserable ourselves.

To join the animal welfare movement contact [email protected], www.peopleforanimalsindia.org