Echeneis naucrates Linnaeus 1758

slender suckerfish

shark remora, striped suckerfish

The Slender Suckerfish, Echeneis naucrates, can sometimes be found swimming freely but more usually it is attached to larger animals, especially sharks and rays.
It attaches by means of a sucker on the top of its head. The Slender Suckerfish feed on scraps left by their hosts, they may also remove parasites from the host's skin.
Markings are variable ranging from conspicuous black, white and grey stripes in younger ones, to plainer grey in older ones.