Jawfish are Perciformes in the family Opistognathidae.
They can be found around coral reefs in the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Gulf of Mexico.
Jawfish live in burrows that they dig in sand. They dig by filling their mouths with sand and then spitting out the sand.
A jawfish's body produces a type of mucus that it uses to hold its burrow together and keep it stable.
It spends a great deal of its time partway in its burrow, with the tail end of its body inside the burrow and only its head jutting out.
Jawfish are carnivores. A jawfish will hover near its burrow and eat animal plankton that pass by.
If it senses danger, it will quickly dart back into its burrow, tail first.
Jawfish are territorial. A jawfish will defend the area around its burrow from other jawfish.
They are small fish.
Jawfish have long bodies with large heads, eyes and mouths. The name "jawfish" comes from these fish's large mouths.
A jawfish has one long dorsal fin.
Jawfish are oviparous - the female lays eggs. The male keep the eggs in his mouths until the eggs hatch.
An animal that protects its eggs or its young by holding them in its mouth is known as a mouthbrooder.
The yellowhead jawfish (Opistognathus aurifrons) lives in the Caribbean Sea, in coral reefs.
It has a yellow head, as its name suggests, and a body that may be light blue, light green or creamy white.
It may be up to about five inches long.
The male yellowhead jawfish builds an elaborately decorated burrow to share with his mate.
There is a large chamber at the end of the burrow, which he decorates with sand, shells, pebbles and small pieces of coral.
The male may dig a small crater around the entrance to his burrow.
If the male sees another jawfish near his burrow, he will rush out of the burrow and stand on his tail. To make himself appear ferocious, he will raise his fins, flare his gill coverings and open his huge mouth in a threatening manner.
The yellowhead jawfish is a popular aquarium fish.