A dark fish that rides attached to sharks and rays by a ridged disc on the top of its head.
To about 86 cm, though most are under 40. Uniformly blackish, brown or grey, and stout for a remora. The sucking disc on top of the head carries sixteen to twenty laminae.
The sharksucker is the one to rule out: far more slender, boldly striped black and white, and it swims free as a matter of course. This fish is usually attached.
Nought to two hundred metres, wherever its host goes. It rides sharks mainly, but also large fish, sea turtles, whales and ships, sitting on the body, on the fins or inside the gill chambers. It feeds on the host’s scraps, on plankton and on parasitic copepods, and younger individuals do more of the parasite picking.
The relationship is not cleanly a partnership. It adds drag to the animal carrying it, which is a cost the host does not choose.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.