Gobiidae
The family of gobiidae which is made up of fish called gobies make up the largest marine family of fish in the world with around 1,950 different species. It is common for gobies to have their pelvic fins fused together. This allows them to use their pelvic fins as a suction device to keep them anchored on a hard surface such as a rock or piece of coral. Gobies often live in association with invertebrates such as sponges and sea urchins in or around corals both soft and hard; however some species live on bare mud and sand. Gobies are typically small fish many do not exceed a total length of 10 cm. Some of the smallest fish in the world belong to this suborder such as the Trimmatom nanus. This is a species found in the Indian Ocean which is only 8-10 mm as an adult. The largest of the Gobiid family is found in the South Atlantic and Caribbean region the Violet Goby or Gobioides broussenetti can grow to a length of 50 cm long, this goby which is purple in color resembles an eel with its elongated anal fin and dorasl fin. Some gobies under the genus of Periophthalmus and Boleophthalmus are practically amphibious, meaning they can breath in and out of water. Species like the Atlantic mudskipper (Periophthalmus barbarus) which can grow to a length of 25 cm can actually breath air. These gobies will skip across the mud of intertidal flats in mangrove swamps in search of food, adults feed mostly on crabs, insects and other arthropods .
While most of the species in this family are found in a marine setting there are some species that inhabit fresh water streams and lakes. Some of which are important to island stream assemblages. Species such as the Red-Tailed Stream Goby (Lentipes concolor) are able to use their fused pelvic fins as a suction device which enables them to ascend rock faces along side waterfalls allowing them to inhabit waters far from the ocean.
Read more about this topic: Gobioidei