Talbot’s Cardinalfish

Flame red, fourteen centimeters, and almost nobody sees it.

Red is the family's default color and it is worth understanding why. Water absorbs red light first: by ten meters most of it is gone, by twenty there is effectively none, and an animal that reflects only red has nothing left to reflect. It reads as black, or as nothing at all. For a fish that works at night and hides by day, red is the cheapest possible invisibility, and it costs nothing to make.

The catch is what happens when a diver arrives with a torch. Under white light at close range the same fish is a brilliant scarlet, which is why the reef looks so different in a photograph with strobes than it does to the eye. The colors were always there; the light was not.

So the entire cardinalfish family, along with the soldierfish and squirrelfish that share their caves, appears drab or invisible to anyone diving without a light, and spectacular to anyone with one.

This species is among the largest of them here, and it stays deep in caves and crevices through the day.