Mustelus mustelus is a common species of shark found in the eastern Atlantic Ocean and the Mediterranean Sea. It is also known as the smooth-hound shark, blue-grey shark, and the common smooth-hound. Other synonyms of Mustelus mustelus include the common houndshark, the Atlantic smooth dogfish, the common dogfish, and the smooth-sided shark. These names are all used interchangeably to describe this shark species. The Mustelus mustelus is a small and relatively harmless species, with a maximum size of around 4 feet. It primarily feeds on small fish, crabs, and other crustaceans and is not considered a threat to humans.