Giant Jawfish

Opistognathus rhomaleus

The giant jawfish (Opistognathus rhomaleus) is the largest species in the jawfish family, found in the eastern Pacific Ocean. Adults reach 35-50 cm and display a mottled brown to grey body with a disproportionately large head and enormous mouth, which is used both for excavating burrows and for mouthbrooding eggs. They inhabit sandy and rubble areas adjacent to rocky reefs at depths of 5-50 meters, constructing vertical burrows lined with small rocks and shell fragments. They typically hover vertically above their burrow entrance, feeding on passing zooplankton and retreating tail-first into the burrow at the first sign of danger. Males incubate fertilized eggs in their mouths for several days until hatching, during which time they cannot feed. Their comical appearance, head-bobbing behavior, and fascinating reproductive biology make them a favorite encounter for divers in the Sea of Cortez and along the Pacific coast of Central America.