Remora
Remora, or Shark Sucker, a slender-bodied fish that attaches itself to larger fish by means of a sucking disk on top of its head. The disk is a modified first dorsal (back) fin. It is oval in shape, and usually has 20 or more crosswise ridges that can be erected to create a vacuum. The remora attaches itself to all larger fish and to turtles, whales, and ships, feeding on scraps left by its carrier. There are about 10 species of remoras. They are found in all tropical seas. In the warmer months, two species are found in United States waters as far north as Cape Cod and San Francisco. One species grows to 36 inches (90 cm) in length; the other, to 18 inches (45 cm).
Remoras belong to the family Echeneidae. The larger species mentioned is Echeneis naucrates; the smaller, Remora remora.