Goby, any fish of the genus Gobius, type of an acanthopterygian family (Gobiidee) of small shore fishes common on temperate and more so on tropical coasts. Some frequent estuaries, and a few live in fresh water. In the type genus the body is scaly, there are two dorsal fins, and the ventrals are united to form a sucking disc, by which these fish can fasten themselves to rocks. The males of some species are not only nest builders; they also watch over the nest after the young are born. There are about 300 species, several of which are British. The largest of these is the Black Goby ( G. niger), and is about 5 inches long. Like the other British forms, it is often taken with a net in rock pools, and all these are frequently kept in aquaria. The White Goby (Latntnculus albus), a small transparent fish with teeth in one row, common in some parts of Britain and the Continent, is said to be the first recorded instance of an annual vertebrate, for the life-term is a single year. The same peculiarity has been observed in allied American genera (Aphya and Cry stalli gobius).