Asked by: Andrew Smith, London

Consciousness is a mystery. It’s impossible to know what an animal, or even another human, is experiencing. We cannot ask a fish, we can only observe it. Fish can learn and have long memories. When stressed by being held in a net, they display ‘emotional fever’, meaning they increase their body temperature.

So do they feel pain? They have some brain structures similar to ours and also have opioid receptors. And if given anaesthetics, they are less affected by noxious stimuli.

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