Suckerfish

The Suckerfish is an uncommon fish introduced in. It can be found in the sea between June and September in the Northern hemisphere and between December and March in the Southern Hemisphere. It can be found at any time of day, and it sells for 1,500 Bells.

Real-world information
The Remora family possess distinctive first dorsal fins that 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. They spend their lives clinging to a host animal such as a whale, turtle, shark or ray. The remora and it's host organism likely possess a mutualistic relationship 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 to be false; in reality, their diets are composed primarily of host feces.