This article published in Aeon looks at the question of sentience in fish.

In me at least, when I really stop and think about it, this raises a creeping feeling of unease.
There is definitely an increasing body of evidence that challenges our sapien-centric claim to being the consciousness boss of things around here.
If even fish are sentient, and have an experiential, aware life….how does this restructure our place in the world and the way we interact with it?

Do fish have a conscious, meaningful (for a fish) experience of the world?
Do they know they are a fish?
Do they experience pain?

There is no argument that the pallium of fish is anatomically less complex than the neocortex of mammals. It is: but that doesn’t mean it lacks adequate complexity to participate in a neural network that produces sentient states. Anatomically, the fish pallium isn’t homogeneous. It has seven distinct divisions based on structural differences in the arrangement of the neurons found within them and, just as divisions of the mammalian neocortex are interconnected, both excitatory and inhibitory neurons interconnect divisions of the fish pallium. Excitatory neurons support positive feedforward and feedback between pallial areas, while inhibitory neurons permit temporal stabilisation and spatial sharpening of neuronal activity. Furthermore, as is the case with the mammalian neocortex, the fish pallium receives several qualitatively different modalities of sensory input, and the different modalities are segregated in the pallium. Finally, the pallium receives nonspecific input from cholinergic, dopaminergic, GABAergic, serotonergic and noradrenergic modulatory systems. These neurotransmitter systems are associated with modulation of arousal and feeling tone – further neurological evidence for a minimal kind of sentience implying that fish can feel pain.

Check out the full article.

Probably, fish cannot think about their thinking (metacognition) like we do, but they almost certainly have some form of phenomenal consciousness. By the very nature of its sensory apparatus, anatomy, physiology, and lived environment, what it feels like to be a fish would be completely unimaginable to us….who is to say it is any the lesser?

Deeper dive: Woodruff, Michael L. (2017) Consciousness in teleosts: There is something it feels like to be a fish. Animal Sentience 13(1)

Photo by Jakub Kapusnak