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Clown trigger fish.

University of Queensland

Reef Fish See Colors Humans Can Only Dream Of

Study reveals how coral reef fish visual systems perceive the color spectrum.

| 2 min read

Study reveals how coral reef fish visual systems perceive the color spectrum.

Coral reef fish come in a stunning array of colors, which double for them as means of camouflage and visual communication. Though we often admire the beauty of these fish, a new study published in Royal Society Open Science finds that humans can’t even begin to appreciate their color variation to the extent that the fish themselves can.

Researchers at The University of Queensland, Australia, set up an experiment in which trigger fish — a group of brilliantly-colored coral reef species — were shown progressively similar colors in the blue region of the spectrum. When they successfully discriminated the colors from one another, they received a reward.

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It became apparent that these fish were able to distinguish colors with vastly greater resolution than humans — they could see clear colors in what, to the human eye, appear as nothing more than blurred boundaries between pairs of neighboring colors.

"Coral reefs are the most colourful environments in the world, and it's now become clear that reef fish see colours we can't," says study senior author Justin Marshall in a press release.

He explains that, while some reef fish, such as the clownfish (i.e. Nemo), can actually see wavelengths that are beyond the spectrum of human perception, like ultraviolet waves, trigger fish “see more or less the same colour range we do but their colour discriminations are different.”

Previous research has shown trigger fish have two types of cones in their eyes, which house three types of visual pigments, allowing them to see the world in different colors. But until now, the extent of their color vision was not fully appreciated.

Marshall is not entirely surprised by how well the trigger fish can discriminate similar colors from one another. As he notes, these fish live in an ocean environment, where a high level of blue color perception would be of great value.

“Ironically, as the colours of the reef change and disappear because of climate change, we are just beginning to understand how reef inhabitants see and experience their vibrant world,” says Marshall.

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