Sharksuckers: Not Just for Sharks! And They Don’t Suck

More properly known as remoras, the “sharksuckers” that famously hitch rides on sharks also stick themselves to tunas, manta rays and other large fishes, turtles, whales, boats and anything else that might move. Including, occasionally, divers. 

white suckerfish remoras (Remora albescens)
Riding the world upside down on a manta ray’s back, a pair of white suckerfish remoras (Remora albescens) employ a suction effect to attach to their host.

 SHARKSUCKERS – REMORAS – USE LARGE SUCTION PADS on the tops of their heads to stick to their hosts, relying on those sharks, rays or whatever to do the heavy work of actually moving.

The suction pads are transformed dorsal fins – that is, the fins normally rising above a fish’s upper surface. As a result, the hitchhiking fishes spend their lives lying on their backs, seeing the world upside-down.


Opinions as to whether they’re good, bad or indifferent for their hosts are mixed. As is, for that matter, about how their hosts feel about them. Some sharks have been observed seemingly encouraging remoras to come on board. But one reason sharks, rays, whales and dolphins leap out of the water may be to get rid of remora freeloaders.

What is clear is that remoras have evolved a niche in the web of life compensating for poor swimming abilities, poor buoyancy control and poor foraging skills.

sharksucker remora Echeneis naucrates
The tradition conception of a remora relationship: A small remora, most likely a sharksucker (Echeneis naucrates), sticks to the side of a Caribbean reef shark. A second one, apparently, glides momentarily just underneath.


It’s known there are eight species found worldwide in family Echeneidae, ranging in size from, say, 12 in/30 cm to some 40 in/3.3 m in length. In casual references, the word “sharksucker” tends to get pasted on all of them. But that’s probably because people tend to be fixated on all things shark.

Actually, some remora species specialize in more-or-less specific hosts. The white suckerfish (Remora albescens) particularly prefers manta rays, the spearfish remora (Remora brachyptera) swordfishes and other billfishes and the marlin sucker (Remora ostechir)…well…marlins. But those are preferences. They pretty much all will attach to nearly any host when the need or opportunity arises.


Google “sharksucker” and you’re likely to be directed to the common remora (Remora remora). It’s a somewhat thick, dark fish classified in the Romora genus. In reality, R. remora is actually far from discriminating, showing a willingness to attach to a wide range of hosts, from sharks and whales to boat hulls.

Another easily Googled “sharksucker,” Echeneis naucrates, resides in the Echeneis genus. It’s also commonly seen, characterized by a slender, light-colored body with a dark stripe running along each side. It’s also open to multiple types of hosts.

sharksucker remora Echeneis naucrates
This midnight parrotfish found itself the carrier of a remora in the Bahamas.

Echeneis naucrates is sometimes also called a “slender suckerfish.” Which is not to be confused with Phtheirichthys lineatus, a rare remora species in a third genus that’s primarily called the “slender suckerfish.” To give P. lineatus its distinguishing characteristic, it’s described as not as host-dependent as other remoras.


They stick, paste, adhere, vacuum-seal themselves to their hosts, but they don’t suck. Somehow, remoras evolved the trait of converting their dorsal fins into relatively large suction pads with as many as 20 movable lamina – layered tissue structures – that they can raise or lower to create suction on their hosts’ surface. Sliding backwards strengthens the seal, swimming forward breaks it.

sharksucker remora Echeneis naucrates
It’s unusual to see a remora’s suction pad. Counter-intuitively, the view is of the top of its head. During a Bahamas dive we encountered this guy swimming around free looking for something – or someone – to attach to. 

Research by biologists at the New Jersey Institute of Technology suggests the suction pad effect is even more complicated. They found that the pads rely on tiny spikes – termed lamellar spinules –that maintain the connection through friction. Uniquely structured blood vessels in the remoras’ heads may facilitate this.

Those tiny spicules may be why the Florida Museum’s article on E. naucrates points out that the fish’s attaching to divers’ legs with “numerous sharp ridges” can be painful. If they’re painful to their fishy hosts, nobody says so.

sharksucker remora Echeneis naucrates
For a moment, it stalked my buddy during a safety stop, but then moved on.


Why remoras do it is a little murky. Conventional wisdom says they ride along to feed off the food scraps that sharks or other hosts scatter about while attacking their prey.

But some sources suggest that they serve a cleaning function, removing parasites and dead skin cells from their hosts. And, that they help maintain their hosts’ overall health by eliminating the food scraps’ bacterial threats.

Keep in mind that manta rays, one prominent host, don’t scatter meaty scraps around – they scoop in plankton. And some studies of remoras’ stomach contents have found that some species include plankton like copepods in their diets, just as mantas do. Whether they clean those copepods off their hosts or just grab them when the fall off is unclear.

And at least some species feed off their hosts’ fecal matter. To what degree remoras dine on fish poop depends on what you read. At bottom, food sources and benefits probably vary according to the species, hosts and situation.


Putting aside feeding issues, the question of why sharksuckers hitch rides has one big answer: It benefits them by letting someone else do all the hard work of cruising the oceans.

Lacking gas bladders, they are poor distance swimmers. Like all fishes, they  need to have water passing through their gills to oxygenate their blood streams. Sharks and tunas accomplish this by constantly swimming – “ram ventilation.”

white suckerfish remoras (Remora albescens)
Click on this screenshot for a short video of a pair of white suckerfish remoras (Remora albescens) mooching rides on a manta ray – and feeling free to move around. © Ralph Fuller

For remoras, hitching rides with fast-moving hosts is ram ventilation with minimal energy expenditure. Remoras can swim for short distances and they can perform the “active ventilation” process of pumping water through their gills. However, their sticky lifestyle lets them meet their needs with somebody else expending the energy.

Additionally, sticking to a shark offers them protection from predators, including, perhaps, the host sharks. By and large, scientists studying the contents of shark stomachs don’t tend to find remoras in them.


  • Practically nothing appears to be known about remora reproduction or mating behavior.
  • Research on remora larvae – the really hard part is finding remora larvae – has shown that little remora fishes start out with regular dorsal fins, which eventually transform into suction pads.
  • Before that happens, for a time remora larvae live in the ocean’s plankton layer, then disappear. They have little hooked teeth protruding from their lower jaws, and it’s surmised that they may take to using those teeth to hook on inside fishes’ gill cavities until the pad develops.
  • Native fishermen through history have been known to use remoras to catch other fishes. By tying a line to a remora’s body and releasing it into deep waters, they pull it in once it’s attached itself to another fish.
  • The word remora can be somewhat confusing, if only because it’s used for everybody in the Echeneidae family, for one genus of several species within the family and for one species in particular. The Remora genus covers six species, among them one the “common remora,” Remora remora.
  • The term “remora” comes from the Greek word for “delay.” When ancient seamen found them attached to their boat hulls, they assumed their presence slowed the boats down. The family name Echeneidae has the same meaning.

PRINCIPAL SOURCES:  Reef Fish Identification Florida, Caribbean, Bahamas, Paul Humann, Ned DeLoach;  Echeneis naucrates, Florida Museum;  Remoras don’t suckNew Jersey Institute of Technology via news; Remora remora,, Animal Diversity Web, University of Michigan; New study proves the remora’s sucker disc is in fact a highly modified dorsal fin / Q&A with taxonomist David Johnson, Smithsonian; Sharksuckers Or Remoras, Echeneis naucrates, Remora brachyptera,, Encyclopedia of Life; The Horrible Natural History of Remoras, Dive Magazine, U.K.; Remora, Remora Genus, Common Remora, et. al., Wikipedia.