Open Water

THE BRAINS OF FISH

A Mexican tetra, Astyanax mexicanus, turns through the darkness.
A Mexican tetra, Astyanax mexicanus, turns through the darkness. The species exists in two remarkably different forms: Sighted, pigmented fish inhabit surface waters, while isolated populations living beneath the limestone of northeastern Mexico have evolved translucent bodies and empty eye sockets. Similar cave-adapted traits have evolved independently in more than 200 fish species worldwide. Despite their radical differences in appearance, blind Mexican tetras remain members of the same species as their sighted counterparts. Photo: Paul Kameen
Words: Paul Kameen

Despite modern assumptions, fish have not always been seen as simple. Across history and culture, they have often been treated with reverence, curiosity—even fear.

In early Christian tradition, the word fish was not just symbolic—it was a cipher for something hidden. Fish appear repeatedly in scripture and religious iconography: loaves and fishes, Jonah’s three days inside the great fish, baptismal water. In these stories, fish often stand in for faith, representing the presence of something deeper, just beyond understanding.

You see echoes of this in other traditions. In Japanese folklore, the catfish Namazu is said to live beneath the earth, thrashing violently and causing earthquakes when stirred. The metaphor is myth, but the pattern is not entirely fiction. In the 1920s, seismologists Shinkishi Hatai and Noboru Abe studied aquarium catfish and found that the animals became unusually restless before earthquakes, jumping or swimming erratically. In their study, the catfish correctly signaled most of the recorded seismic events.

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