Why Do Angler Fish Have Lights?

The light attracts small fish, which the angler fish catches and eats. This "fishing rod" is the front spine of the fish's dorsal fin. If an enemy approaches the angler fish shoots a luminous fluid from this spine and stuns the attacker. Some light penetrates the ocean down to a depth of 3,200 feet (975 m). Fish with light-producing mechanisms are most common at that level or higher. They have eyes that are well developed, enabling them to see in semidarkness. Fish living at greater depths, where there is no light at all, have atrophied eyes and no light-producing ability. Some deep-sea fish have a stomach that glows. The sea is lighter at the surface, so enemies attacking from below can't see them easily.