<Tr> <Td_colspan="2"> <P> Echeneididae </P> </Td> </Tr> <P> The remoras / ˈrɛmərəz /, sometimes called suckerfish, are a family (Echeneidae) of ray - finned fish in the order Perciformes . They grow to 7--75 cm (2.8 in--2 ft 5.5 in) long . Their distinctive first dorsal fins take the form of a modified oval, sucker - like organ with slat - like structures that open and close to create suction and take a firm hold against the skin of larger marine animals . The disk is made up of stout, flexible membranes that can be raised and lowered to generate suction . By sliding backward, the remora can increase the suction, or it can release itself by swimming forward . Remoras sometimes attach to small boats, and have been observed attaching to divers as well . They swim well on their own, with a sinuous, or curved, motion . </P> <P> Remora front dorsal fins have evolved to enable them to adhere by suction to smooth surfaces and they spend their lives clinging to a host animal such as a whale, turtle, shark or ray . It is probably a mutualistic arrangement as the remora can move around on the host, removing ectoparasites and loose flakes of skin, while benefiting from the protection provided by the host, and the constant flow of water across its gills . Although it was initially believed that remoras fed off particulate matter from the host's meals, this has been shown a falsehood; in reality their diets are composed primarily of host feces instead . </P> <P> Remoras are tropical open - ocean dwellers, but are occasionally found in temperate or coastal waters if they have attached to large fish that have wandered into these areas . In the mid-Atlantic, spawning usually takes place in June and July; in the Mediterranean, it occurs in August and September . The sucking disc begins to show when the young fish are about 1 cm (0.4 in) long . When the remora reaches about 3 cm (1.2 in), the disc is fully formed and the remora can then attach to other animals . The remora's lower jaw projects beyond the upper, and the animal lacks a swim bladder . </P>

What are the fish that are on sharks