Opistognathidae (opisto = "behind", gnath = "mouth"), commonly referred to as jawfishes, are classified within the order Perciformes, suborder Percoidei. They are found throughout shallow reef areas of the Atlantic and Pacific Oceans, and the Gulf of Mexico.
Physically similar to blennies, jawfish are generally smaller-sized fish with an elongated body plan. Their heads, mouths, and eyes are large in size relative to the rest of their bodies. Jawfishes possess a single, long dorsal fin with 9-12 spines and a caudal fin that can be either rounded or pointed.
Jawfishes typically reside in burrows they construct in sandy substrate. They will stuff their mouths with sand and spit it out elsewhere, slowly creating a tunnel. Using the protection of these burrows, these fish will hover, feeding on plankton or other small organisms, ready to dart back in at the first sign of danger. They are territorial of the area around their burrows.
Jawfishes are mouthbrooders, meaning their eggs hatch in their mouths, where the newborn fry are protected from predators.
The gestation period varies between species. Goldspec jawfish (Opisthognagthus sp.) typically keep their clutch of eggs for 8-10 days before hatching.
