Fish could have emotions and consciousness, biologists find

Fish could have emotions and conciousness, according to new research published in Proceedings of the Royal Society of London, Biological Sciences, which has for the first time observed in fish a phenomenon known as emotional fever – the increase in body temperature when subject to stress – which has been controversially linked to consciousness.

Researchers from the Universitat Autònoma de Barcelona, together with scientists from the universities of Stirling and Bristol (United Kingdom), observed an increase in body temperature of between two and four degrees in zebrafish, when these are subjected to stressful situations.

Until now emotional fever had been observed in mammals, birds and certain reptiles, but never in fish.

For this reason fish have been regarded as animals without emotions or consciousness, but the experiment, with 72 zebrafish, has brought this view into question.

The researchers divided the fish into two groups of 36 and they were placed in a large tank with different interconnected compartments with temperatures ranging from 18ºC to 35ºC.

The fish in one of these groups – the control group – were left undisturbed in the area where the temperature was at the level they prefer: 28ºC. The other group was subjected to a stressful situation: they were confined in a net inside the tank at 27ºC for 15 minutes. After this period the group was released. While the control fish mainly stayed in the compartments at around 28ºC, the fish subjected to stress tended to move towards the compartments with a higher temperature, increasing their body temperature by two to four degrees. The researchers point to this as proof that these fish were displaying emotional fever.

Scientists differ on the degree to which fish can have consciousness. Some researchers argue that they cannot have consciousness as their brain is simple, lacking a cerebral cortex, and they have little capacity for learning and memory, a very simple behavioural repertoire and no ability to experience suffering. Others contest this view, pointing out that, despite the small size of the fish brain, detailed morphological and behavioural analyses have highlighted homologies between some of their brain structures and those seen in other vertebrates, such as the hippocampus (linked to learning and spatial memory) and the amygdala (linked to emotions) of mammals.

In the words of Sonia Rey, of the Institute of Aquaculture, University of Stirling and the UAB’s Institute of Biomedicine and Biotechnology (IBB), “these findings are very interesting: expressing emotional fever suggests for the first time that fish have some degree of consciousness”.

7 Responses to Fish could have emotions and consciousness, biologists find

  1. James G says:

    I’ve kept cichlids for over 10 years. There are so many fish in the genus of cichlidae and they are all remarkably intelligent. I’ve had many that recognized my face and would gently take food from my fingers but if someone else tried they either wouldn’t come near or would take the food very aggressively. Also they have done studies on African cichlids that show they have very intricate hierarchies and they not only remember their place in this but they remember other fishes place in the hierarchy.

  2. peter warren says:

    so… fish leaving water with a temperature LOWER than what they prefer for warmer water is emotional fever? in that case, i have a new experiment for you. starve fish for a while, and then observe them eating in comparison to normally fed fish. i bet they will eat more and faster… that is stress eating!

    others would call that behavior “instinct”. leaving less habitable zones for more habitable zones.

    i strongly disagree with your interpretation of the experiments result.

  3. Roger Davis says:

    Interesting experiment. I hope behavioral expect
    Continue. It is too early to see what such findings mean.
    But the possibility that fish are neuropsychologically more complicated than biologists have thought tickles my imagination.

  4. Zephir says:

    How the scared fish behaves
    How the fish in playful mod behaves:

    The scientists should visit YouTube more often… 😉

  5. Anonymous says:



  6. No Name says:

    I keep goldfish myself. They are very personable and will swim up to anyone to say “Hi!” They know when it is feeding time because they see me on that side of the tank in the cabinet getting out their food. I soak it first so they know what the spoon looks like as well. They get super excited and kne even spits water at me when I open the lid he’s so excited for food. Fish are smarter than people give them credit for. Those who have no kept fish or not kept them very long or healthy just so not know what they are missing or what their personalities become to be. Betta fish? One of THE friendliest fish to humans you will ever meet. After hey recognize you and they settle into their home, they will swim right at the front of glass and swim back and forth wiggling their bodies. They get so excited when they see people and especially when they get fed! I had one that would kiss my finger before I went to bed <3

  7. mark says:

    I agree with No Name. My girlfriend’s goldfish responded well and recognised her. She could move the elder fish to another tank by lifting it out by hand. The fish laid still. The eldest goldfish also learned how to attract her attention when she was late feeding them by noisily sucking at the water surface. The others then copied this behaviour. In effect my girlfriend was trained to respond to a command by fish.

    It seems to me that goldfish can make the following deductions:

    1. That big thing outside the invisible barrier is the thing that causes me to be fed. It’s a nice thing.
    2. It’s a living thing like me.
    3. It can probably hear like I can.
    4. I know I respond to noise.
    5. It can probably respond to noise too.
    6. I can make noise myself. I remember how to do this.
    7. If I make a noise the big thing might respond.
    8. This response would be positive and result in food.

    Emotions and consciousness! These seem the last distinction science holds between human and beast now that language and tool using/making has been seen in animals.

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