Gobius is a collective term for 21 species of fish in the Black Sea. Some are quite small - 3-5 cm in length and 1-5 g in weight and are important food for other species. There are also larger ones that are caught for food because of their tasty meat. They have many bones, one of which - at the back of the head looks like a cross. Almost all species make nests for their eggs, which the males guard until the young fish hatch.