Do Fish Feel Pain? Here’s What Science Says 
© Evgeniia / stock.adobe.com
Numerous studies have answered the question of whether fish feel pain with a yes.
Aquarium enthusiasts and animal-loving anglers might at some point ponder: do fish feel pain? Since fish can’t speak, finding a satisfactory answer is not straightforward. However, a foray into science does offer better insight into the pain perception of fish.
Table of contents
Biological Basics: How Is Pain Generated?
The mere thought of pain often elicits negative feelings in people. Yet, pain (algesia) certainly has its raison d’être, serving as a crucial warning function within the body.
Pain signals to organisms to withdraw from the pain-inducing stimulus to avoid potential harm from the source of pain.
To experience pain, an organism needs pain receptors in its body. These so-called nociceptors react to various stimuli that can trigger a pain signal, including:
- chemical (toxins),
- mechanical (injuries), or
- thermal stimuli (heat or cold).
However, simply having pain receptors is not enough for an organism to consciously perceive pain. First, the received signal must be processed.
This vital role is played by the brain. It receives pain signals from the body through neural pathways and interprets them, happening, for instance, in the somatosensory cortex or the anterior cingulate cortex.
How Humans Express Pain
Humans have a complex perception of pain, hence they experience and react to pain in different ways.
How humans respond to pain is influenced by various factors:
- Location of pain: such as headaches or stomach aches
- Duration of pain: acute or chronic
- Quality of pain: sharp or tormenting
Examples of Different Pain Responses
The reflexive withdrawal of a hand upon touching a hot pot is a pain response that occurs even before conscious perception of pain.
In contrast, pain behaviour that can occur later, such as losing your appetite gradually over a period of sustained headaches.
How Do Fish Experience Pain?
Although fish are not mammals, it is assumed that they have a similar capacity for pain as humans since they also belong to the vertebrates.
Science on Pain Receptors in Fish
Scientists have conducted studies on the anatomy and physiology of animals to determine if fish possess the basic requirements for pain development. They compared the nervous systems of humans and fish, searching for nociceptors.
The findings reveal that not only humans but also fish have the anatomical and physiological conditions to receive painful stimuli.
The fish examined were shown to have not only the necessary pain receptors but also brain areas resembling those of mammals and birds.
Does Fishing Cause Pain to Fish?
The book “Do Fish Feel Pain?” by biologist Victoria Braithwaite includes a detailed map of more than 20 pain receptors in the mouths and heads of fish, encompassing areas where an angler’s hooks penetrate. But do fish actually feel pain?
© Pablo Santos Somos / stock.adobe.com
The Pain Perception of Fish
While fish have the ability to feel pain, the question of whether they have a conscious perception of pain was addressed in further studies.
Researchers tested whether and how fish respond to painful stimuli, such as changing water temperatures or injecting an active substance under anaesthesia into their lips, resembling the effect of nettle contact.
The resulting behaviours suggested that fish feel pain: swimmers turned to the other side or rolled in circles, and others rubbed their mouths against the walls of the aquarium or stopped eating altogether.
A Hot Bath Leaves Its Mark
An additional study showed that goldfish exposed to heat subsequently displayed anxious behaviour at high temperatures.
This response was interpreted by researchers as evidence not only that the creatures feel pain but can also remember it.
Learn in the Aquatics Magazine from zooplus how to test water hardness in your aquarium.
Counterarguments: Do Fish Not Feel Pain After All?
Though much suggests that fish feel pain, there are also conflicting opinions. These are the main arguments against fish feeling pain:
- Absence of the Cerebral Cortex: Some scientists argue against fish pain perception due to the absence of the cerebral cortex, which is necessary for conscious pain awareness. However, other areas could take over this function in fish.
- Absence of C-fibres: Vertebrates have two types of nociceptors: A-delta fibres and C-fibres. C-fibres transmit sharp pain signals to the brain. To date, researchers have not yet identified these receptors in flatfish such as sharks and rays. With a vast diversity of species, not all fish types have been included in studies.
- No Pain After Surgery: Humans often feel pain following surgical procedures. In contrast, fish showed no behavioural changes after skull drilling operations, leading some researchers to suggest that fish do not feel pain.
Conclusion: Can Fish Feel Pain or Not?
Since fish cannot speak, scream, or cry, a definitive answer to the pain question is impossible. However, there is considerable evidence supporting the idea that fish can unconsciously feel pain.
For animal welfare, the scientific investigation into questions like “Do fish feel pain or not?” remains vital. Only with accurate knowledge of how fish perceive their environment can a species-appropriate and pain-free husbandry be ensured. It is also crucial to acknowledge that fishing hooks touch parts of the fish’s body where pain receptors exist. This knowledge could, in the long run, contribute to the prohibition of such methods in fishery.
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At the Justus-Liebig-University of Giessen I was extensively trained as a veterinarian and was able to gain experience in various fields such as small animal, large animal and exotic animal medicine as well as pharmacology, pathology and food hygiene. Since then, I have been working not only as a veterinary author, but also on my scientifically driven dissertation. My goal is to better protect animals from pathogenic bacterial organisms in the future. Besides my veterinary knowledge, I also share my own experiences as a happy dog owner and can thus understand and enlighten fears and problems as well as other important questions about animal health.
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