Tiny tooth-like spikes on the disc slats

How does a riding remora breathe?

It lets the passing water flow over its gills

What did the 2020 blue whale study find?

Remoras pick spots that cut their drag by up to 84%

Remoras ride anywhere on the whale

Remoras slow whales down by half

How can you tell a live sharksucker from a common remora?

A dark side stripe edged in white

What could a 2017 remora-inspired disc do?

Hold up to 340 times its own weight

Remora

Q: How to identify Remora?

Look at body shape, where the fins sit and their outline, mouth position, stripes and spots. Young fish and breeding adults can wear different patterns, and aquarium color varieties can look nothing like wild fish. Fish Identifier: upload a photo and compare the visible details.

Q: What does Remora eat?

Remoras eat scraps from their host's meals, small fish and tiny parasites. The common remora mostly eats parasitic copepods, which are small crustaceans.

Q: What is a remora fish?

A remora is one of 8 species of fish in the family Echeneidae that hitch rides on bigger animals using a suction disc on top of the head. The disc is a changed dorsal fin.

Q: Why do remoras attach to sharks?

For a ride that saves energy, food scraps and parasites to eat, and a better chance of meeting a mate. Companion fish may also gain protection from predators by staying close to a big host.

Q: How does a remora stick to a shark?

Muscles raise slats in its disc, which creates suction, while tiny spinules on the slats grip by friction. It took about 17.4 N to pull a sharksucker off shark skin.

Q: Are remoras parasites?

Not exactly. They don’t suck blood; they eat scraps, small fish and parasites. But riders add drag, and some have been seen pushing into body openings of manta rays. Scientists say the relationship can shift between helpful and harmful for the host.

Q: What do remoras eat?

Small fishes, bits of their hosts’ meals and the hosts’ parasites. The common remora mainly eats parasitic copepods, and young sharksuckers sometimes clean parasites off reef fish.

Q: Can a remora stick to a person?

Yes. Sharksuckers have been reported following divers and attaching to their legs. They are harmless, but the rough disc can hurt. Don’t try to touch or catch them; watch from a distance.

Q: How big do remoras get?

The common remora is usually about 40 cm long and at most 86.4 cm. The live sharksucker can reach 110 cm, and the marlin sucker only about 40 cm.

Q: Are remoras endangered?

No. The common remora, live sharksucker and whalesucker are listed as Least Concern on the IUCN Red List (assessed in 2012).

Remoras (family Echeneidae) are 8 species of slim marine fish that hitch rides on sharks, rays, whales, turtles and big bony fish in warm seas worldwide. On top of the head they carry an oval suction disc: a front dorsal fin rebuilt into rows of spiny slats. The common remora (Remora remora), usually about 40 cm long, is the model on this page.

Also known as Common remora (Remora remora), Shark sucker, Diskfish

Remora abilities

17.4 N pull to unstick it from shark skin
A remora swims up to a big animal, presses its disc on and holds tight. Pulling a sharksucker off shark skin took about 17.4 N, like lifting a 1.8 kg bag.
- In tests, it took more force to pull sharksuckers off shark skin (17.4 N) than off smooth plastic (11.2 N), because the spinules catch on the rough skin.
- Muscles raise the slats to make the suction and can lower them again, so the remora can let go and move.
- Remoras ride sharks, rays, big bony fish, turtles, whales, dolphins and even ships. Sharksuckers have been reported attaching to divers’ legs.
Force needed to pull a sharksucker off
Shark skin17.4 N
Smooth plastic11.2 N
Rough shark skin gives the spinules something to grip.
Sources [6, 7, 8]
≈185× suction boost when tugged
X-ray the disc: rows of slats topped with tiny spikes. At rest the suction is gentle, but when the host tugs, it can rise about 185 times.
- Resting suction averaged just 0.5 kPa below the surrounding water pressure. When sharksuckers were pulled backwards, as a swimming host would do, it rose to 92.7 kPa below on smooth plastic.
- On shark skin the spinules dig in for friction, so less suction was needed (46.6 kPa below), yet the grip was stronger.
- Touch sensors in the soft lip of the disc may tell the remora the moment it makes contact.
Suction inside the disc
Tugged, smooth plastic92.7
Tugged, shark skin46.6
Resting0.5
On shark skin, spinule friction does part of the work.
Sources [2, 4, 6]
Copepods main food of the common remora
Riding close to a hunter means leftovers. Remoras dart out for scraps and pick off tiny parasites.
- Sharksuckers eat small fishes, bits of their hosts’ prey and the hosts’ parasites.
- The common remora feeds mainly on parasitic copepods, small crustaceans.
- Young sharksuckers sometimes set up cleaning stations on reefs and clean parasites off parrotfishes.
Sources [7, 8, 10]
3.7–5.7% extra oxygen to pump instead
On a moving host, a remora stops pumping its gills and lets the passing water flow through its open mouth instead.
- Sharksuckers switched to ram ventilation once water flowed past at 10–50 cm per second, depending on their size.
- Pumping used 3.7–5.7% more oxygen than ram breathing. Faster water did not raise the cost any further.
- The study concluded that pumping costs sharksuckers less than had been reported for fish in general.
Sources [9]
up to 84% less drag in the best spotsStill debated
On blue whales, remoras pick sheltered spots, then slide or skim along the skin to stay in the whale’s slipstream.
- Cameras on blue whales showed remoras gathering where the flow separates behind features on the skin, cutting drag by up to 71–84% compared with open water.
- They moved about by sliding (attached) and skimming (just above the skin). Skimming cut drag by 50–72% in some spots, and a Venturi effect may help keep them close.
- An earlier computer study of a single attached sharksucker found the host’s flow made little difference, so scientists are still working out how much drag guides where remoras ride.
Drag saved on a blue whale
Attached in the best spots71–84%
Skimming (some spots)50–72%
Compared with open water, from computer models of a swimming blue whale.
Sources [11, 14]
1,460 m deepest remora on record
Remoras go where their hosts go. One common remora rode a whale shark down to 1,460 m, where the water was 3.6 °C.
- A study of deep-diving whale sharks and Chilean devil rays found common remoras and pilot fish staying with their hosts far below the sunlit zone.
- A pilot fish was filmed at 900 m (7.5 °C) on the way back up from the same dive.
- Common remoras usually live in the top 200 m. How they cope with the cold, dark and pressure down deep is unknown.
How deep is that?
Remora on a whale shark1,460 m
Pilot fish, same dive900 m
Usual remora depth limit200 m
Sources [10, 15]
≈1 year young sharksuckers swim free
Remoras can swim on their own. Young sharksuckers live free for about a year, and adults often swim in groups over reefs.
- Sharksuckers hatch at 4.7–7.5 mm long and swim free until they are about 3 cm long, then start attaching to hosts.
- Adult sharksuckers are often seen in free-swimming groups over shallow coral reefs. The open-ocean Remora species are much pickier about their hosts.
- Without a swim bladder, and as fairly poor swimmers, they still rely on hosts to travel far.
Sources [3, 7]
Jaw to tail the sharksucker’s side stripe
Sharksucker or common remora? Scan the side: the sharksucker has a dark stripe edged in white, while the common remora is plain dark grey-brown.
- The live sharksucker’s broad dark stripe runs from the jaw to the base of the tail fin, with white edges.
- Its tail is black with white corners, and its back and belly fins are dark with white margins.
- The common remora is dark brownish grey all over, with no stripe.
Sources [7, 10]

Tap a pin on the model or a part below.

up to 26 slats (lamellae)
- An oval disc on top of the head. It is the remora’s front dorsal fin, completely rebuilt: each slat (lamella) grows from a fin spine.
- Remoras have as many as 26 slats, split into left and right halves down the middle of the disc.
- The disc’s soft rim holds push-rod touch sensors. They were the first found in any fish; before, they were known only from monotremes (the platypus and echidnas).
- The grip holds even on fast-swimming hosts, despite strong drag from the passing water.
Sources [1, 2, 3, 4, 5]
2–4 rows of spinules on each slat
- Muscles tip the slats up or down. Raised slats turn the disc into a chamber with lower pressure than the water outside, so the sea presses the remora on.
- Each slat carries 2–4 rows of tiny, backward-pointing spikes called spinules, made of mineralised tissue like little teeth.
- Spinules grip by friction, mainly on rough skin such as a shark’s. As a remora grows, its slats gain more rows and more spinules.
Sources [1, 2, 6]
Underbite lower jaw sticks out
- The lower jaw sticks out well beyond the upper jaw.
- The jaws carry many small, pointed teeth in brush-like patches (villiform teeth).
- Young sharksuckers grow small teeth in the upper jaw and larger ones in the lower jaw.
Sources [7]
- Sharksuckers eat small fishes, bits of their host’s meals and the host’s parasites.
- They also catch free-living crustaceans such as crabs, and squid.
Sources [7, 8]
10–50 cm/s flow needed for ram breathing
- At rest in still water, a sharksucker pumps water over its gills itself.
- Once the water rushes past at 10–50 cm per second (depending on its size), it stops pumping and lets the flow do the work. This is called ram ventilation.
- Pumping costs it only 3.7–5.7% more oxygen than ram breathing.
Sources [9]
None swim bladder
- The sharksucker has no swim bladder, the gas bag many fish use to float.
- It is also a fairly poor swimmer, so it relies on hosts to get around.
- The common remora feeds mainly on parasitic copepods, small crustaceans that live on big fish.
Sources [7, 10]
86.4 cm longest common remora
- The common remora is dark brownish grey and usually about 40 cm long, at most 86.4 cm.
- Its relative the live sharksucker reaches 110 cm.
- An attached remora is shaped like a streamlined body, so the water drags on it only a little: probably too little to pull it off, even on a fast host.
Sources [8, 10, 11]
22–26 rays in the second dorsal fin
- Behind the disc, the second dorsal fin and the anal fin are long and mirror each other: 22–26 and 22–24 soft rays in the common remora.
- In the live sharksucker the tail is black with distinct white corners.
- Some fishers tie a line to the narrow base of a remora’s tail, let it go and haul it back with whatever it sticks to.
Sources [7, 8, 10]
≈ half of filmed sharks had companion fish
- Common remoras mostly ride open-ocean sharks, billfishes such as marlins, and swordfish.
- Each species has favourites: the whalesucker rides only whales and dolphins, and Remora albescens seems to depend on manta rays.
- In a camera survey of 7 shark species in three oceans, almost half of the sharks had companion fish.
- On blue whales, remoras gather where the flow separates behind bumps on the skin, which cuts their drag by up to 71–84%.
Sources [3, 12, 13, 14]

Real remoras

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

Live sharksuckerSlender, with a broad dark side stripe edged in white and a black tail with white corners. Up to 110 cm long.Rides almost anything, or swims free over reefsLive sharksucker with its disc on show, St. John, U.S. Virgin Islands. Photo: NOAA Photo Library (NOAA CCMA Biogeography Team), CC BY 2.0
Common remoraDark brownish grey all over, usually about 40 cm long and at most 86.4 cm, with a disc of slats on its head.Open ocean; mostly on sharks, billfishes and swordfishCommon remora (Remora remora), NOAA photo. Photo: NOAA CCMA Biogeography Team, Public domain
Live sharksuckerSlender, with a broad dark side stripe edged in white and a black tail with white corners. Up to 110 cm long.Rides almost anything, or swims free over reefsLive sharksucker swimming free, U.S. Virgin Islands. Photo: NOAA Photo Library (NOAA CCMA Biogeography Team), CC BY 2.0
Live sharksuckerSlender, with a broad dark side stripe edged in white and a black tail with white corners. Up to 110 cm long.Rides almost anything, or swims free over reefsSharksucker swimming with a parrotfish, Thailand. Photo: portioid, CC BY-SA 4.0
Green turtle with a sharksuckerPhoto: shahar chaikin, CC BY 4.0
Hawksbill turtle with remoras, northern EgyptPhoto: SEJanssen, CC BY-SA 4.0
Green turtle with remoras, Red Sea, EgyptPhoto: Kora27, CC BY-SA 4.0
Sperm whale mother and calf off Mauritius; the calf carries remorasPhoto: Gabriel Barathieu, CC BY-SA 2.0

Remora by the numbers

Measured by scientists and museums, with comparisons you can picture.

Length (common remora): up to 86.4 cm; usually about 40 cm; The live sharksucker reaches 110 cm⁠[10, 8]
Species: 8; in the remora family, Echeneidae⁠[3]
Disc slats: up to 26; each one began as a fin spine⁠[3, 1]
Pull to unstick: 17.4 N; sharksucker on shark skin; 11.2 N on smooth plastic; About the pull of lifting a 1.8 kg bag⁠[6]
Strongest suction: 92.7 kPa; below the surrounding water pressure, when tugged; 0.5 kPa at rest; About 185 times the resting suction⁠[6]
Drag saved: up to 84%; in the best spots on a blue whale⁠[14]
Deepest ride: 1,460 m; with a whale shark, at 3.6 °C⁠[15, 10]; Deepest ride1,460 mUsual depth limit200 m
Oxygen cost of pumping: +3.7–5.7%; extra oxygen a sharksucker uses to pump its gills instead of ram breathing⁠[9]
Longest stay on one host: 87 days; a whalesucker pair on one spinner dolphin⁠[16]
Early fossil remora: < 32 million years; Opisthomyzon from Switzerland, with its disc behind the head⁠[17]

Remora myths and facts

Sailors’ tales, ‘bloodsucker’ rumours and real science. Which is which?

0 of 8 answered

“A remora can stop a ship.”
“A remora’s suction disc is a changed fin.”
“Remoras suck blood from their hosts.”
“Remoras always help their hosts by cleaning off parasites.”
“A remora sticks on by suction alone.”
“Remoras only ride sharks.”
“People have used remoras to go fishing.”
“Remoras stay in shallow water.”

Remora records

Superlatives from remora studies, each checked against its source.

Deepest remora on record
1,460 m
Common remora on a whale shark
water 3.6 °C; a pilot fish reached 900 m on the same dive⁠[15]
Best seat on a blue whale
up to 84%
Remoras on blue whales
less drag than in open water, in the most popular spots⁠[14]
First proof of a faithful ride
87 days
Whalesucker pair on a spinner dolphin
another pair stayed 47 days; Fernando de Noronha, Brazil⁠[16]
First fish with push-rod touch sensors
2020
The remora’s disc lip
these sensors were known before only from the platypus and echidnas⁠[4]
Early fossil remora
< 32 million years
Opisthomyzon glaronensis, Switzerland
its disc sat behind the head and had no spinules⁠[17]
Remora-inspired super grip
1,391×
MUSAS device (2025)
its own weight, on soft, wet surfaces; the 2017 robot disc managed 340×⁠[21, 5]

A day riding with a remora

Most remoras spend their days on the move with a host. These are the jobs in a remora’s day, from studies of real riders.

Hitching on
Find a ride
A remora swims up to a big animal and presses its disc to the skin. On blue whales, remoras gather where the flow is calmest.⁠[6, 14]
Cruising
Breathe for free
With water rushing past at 10–50 cm per second, it stops pumping its gills and lets the flow through its mouth.⁠[9]
Moving about
Slide and skim
It can slide along the skin while attached, or skim just above it, staying in the low-drag zone.⁠[14]
Snack time
Grab leftovers
When the host feeds, a remora may grab scraps of its meal, or pick tiny parasitic copepods off the skin.⁠[8, 10]
Deep dive
Hang on tight
If the host dives, the remora goes too. One stayed on a whale shark down to 1,460 m.⁠[15]
Meeting up
Find a partner
Riding the same host helps remoras meet. Two whalesuckers rode side by side on one dolphin’s belly for 87 days and were probably a breeding pair.⁠[16]

Growing up remora

From a drifting egg to a hitchhiker, based mostly on the live sharksucker.

Spring and summer
Eggs in open water
Sharksuckers spawn in spring and summer in most places, and in autumn in the Mediterranean. Their large, round eggs drift in the sea. In the Gulf of Mexico, spawning peaks in August.⁠[7, 22]
Hatching
Tiny larva
Hatchlings are only 4.7–7.5 mm long, with a big yolk sac and eyes that have no colour yet.⁠[7]
Growing
The disc forms
As the young fish grows, the front dorsal fin spines turn into the slats of the disc, and each slat gains more spinules.⁠[7, 1]
≈1 year, ≈3 cm
First ride
Young sharksuckers live free for about a year, until they are about 3 cm long, then start attaching to hosts.⁠[7]
Adult
Bigger riders, bigger hosts
Females grow more slowly but end up bigger than males (on average about 60 cm against 48 cm at full size). The bigger the sharksucker, the bigger its host tends to be.⁠[22]

Remora vs sharksucker vs pilot fish

Three famous shark companions. Only two of them can stick.

Common remora vs live sharksucker vs pilot fish
	Common remora	Live sharksucker	Pilot fish
Scientific name⁠[10, 8, 23]	Remora remora	Echeneis naucrates	Naucrates ductor
Family⁠[10, 7, 23]	Echeneidae (remoras)	Echeneidae (remoras)	Carangidae (jacks)
Suction disc⁠[10, 7, 23]	Yes	Yes	No
Longest⁠[10, 8, 23]	86.4 cm	110 cm	70 cm
Looks⁠[10, 7, 23]	Plain dark brownish grey	Dark side stripe edged in white	Bluish with 6–7 dark bars
Main hosts⁠[3, 24, 15, 8, 23]	Open-ocean sharks (whale sharks too), billfishes, swordfish	Almost anything: sharks, rays, bony fish, turtles, whales, ships	Sharks, rays, big bony fish, turtles
Usual depth⁠[10, 8, 23]	0–200 m	1–85 m	0–300 m
Deepest seen with a host⁠[15]	1,460 m	Not known	900 m
IUCN Red List⁠[10, 8, 23]	Least Concern	Least Concern	Least Concern

Pilot fish are jacks, not remoras. Their young often shelter under jellyfish and drifting seaweed.

Robots inspired by the remora

Engineers copy the remora’s disc to build grippers that stick under water and let go when told.

340×
its own weight
A 3D-printed disc with carbon-fibre spinules, modelled on the live sharksucker, held up to 340 times its own weight and let a small robot hitchhike, even on shark skin (2017).⁠[5]
≈60%
better than a live remora
A simple copy of the disc held better as slats were added, and on shark-skin-like roughness it beat the grip of live remoras by almost 60% (2019).⁠[25]
1,391×
grip-to-weight ratio
A 2025 device built on remora tricks sticks to soft, wet surfaces such as the lining of the gut, to carry tiny sensors and slow-release medicines.⁠[21]

These are research devices, tested in the lab and in animal studies.

Are remoras endangered?

No. The common remora and its relatives are listed as Least Concern, but they depend on big hosts that are in trouble in many places.

IUCN Red List

Least Concern (LC)

Trend unknown

The common remora, the live sharksucker and the whalesucker are all listed as Least Concern. Common remoras live in warm seas worldwide.⁠[10, 26, 8, 12]

IUCN Red List, assessed 23 August 2012

Threats

Losing their hosts
Remoras need big animals to ride. Scientists warn that falling numbers of hosts could pull down their companion fish too.⁠[13]
Changing seas
Whether sharks carry companion fish depends on sea temperature, salinity and wind, all of which climate change can alter.⁠[13]
Fishing
Common remoras and sharksuckers are caught in some fisheries and by sport anglers.⁠[10, 8]

What’s helping

Protected areas
Across three oceans, sharks in partly protected areas were more likely to have companion fish, and in strongly protected areas they had more of them.⁠[13]
Protecting hosts
Sharks, rays, turtles and whales carry remoras with them, so protecting the hosts protects the riders too.⁠[13]
Divers’ observations
Photos and videos from divers and researchers keep revealing new remora behaviour, such as the 2026 reports from manta rays.⁠[27]

Other remoras

Live sharksucker (Echeneis naucrates)Least Concern
Reef and coastal remora; assessed in 2012.⁠[8, 26]
Whalesucker (Remora australis)Least Concern
Rides only whales and dolphins; assessed in 2012.⁠[12, 26]

Remora quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

What is a remora’s suction disc made from?

Remora field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Remoras eat scraps from their host's meals, small fish and tiny parasites. The common remora mostly eats parasitic copepods, which are small crustaceans.

Primary Foods

parasitic copepods
scraps from the host's meals
small fish
Foraging Method: Scavenging

Ecological connections

Tiger SharkHost
Hitches rides on big sharks like this one and can grab scraps from their meals.
Giant Oceanic Manta RayHost
Some remoras ride on manta rays. Scientists are still studying whether this helps the manta or bothers it.
Green Sea TurtleHost
Sometimes rides on sea turtles for a free trip. Scientists have not shown that this helps the turtle.

Safety

Danger 1/5 · Very low

Remoras are harmless, but their rough suction disc can hurt. Don't try to touch or catch them, and stay away from the big animals they ride. Watch from a distance, and tell an adult if one sticks to you.

Traits

Collections

Fish

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Echeneidae
Genus: Remora

Also known as

Common remora (Remora remora) · Shark sucker · Diskfish · Remora Fish · Suckerfish

Sources for these remora facts

28 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Remora?

Look at body shape, where the fins sit and their outline, mouth position, stripes and spots. Young fish and breeding adults can wear different patterns, and aquarium color varieties can look nothing like wild fish. Fish Identifier: upload a photo and compare the visible details.

How long is Remora?

30-86.4 cm

How much does Remora weigh?

0.5-2.5 kg

How long does Remora live?

5-10 years

What does Remora eat?

Remoras eat scraps from their host's meals, small fish and tiny parasites. The common remora mostly eats parasitic copepods, which are small crustaceans.

Where is Remora usually found?

Marine

How deep can Remora go?

1460 m

What is a remora fish?

A remora is one of 8 species of fish in the family Echeneidae that hitch rides on bigger animals using a suction disc on top of the head. The disc is a changed dorsal fin.

Why do remoras attach to sharks?

For a ride that saves energy, food scraps and parasites to eat, and a better chance of meeting a mate. Companion fish may also gain protection from predators by staying close to a big host.

How does a remora stick to a shark?

Muscles raise slats in its disc, which creates suction, while tiny spinules on the slats grip by friction. It took about 17.4 N to pull a sharksucker off shark skin.

Are remoras parasites?

Not exactly. They don’t suck blood; they eat scraps, small fish and parasites. But riders add drag, and some have been seen pushing into body openings of manta rays. Scientists say the relationship can shift between helpful and harmful for the host.

What do remoras eat?

Small fishes, bits of their hosts’ meals and the hosts’ parasites. The common remora mainly eats parasitic copepods, and young sharksuckers sometimes clean parasites off reef fish.

Can a remora stick to a person?

Yes. Sharksuckers have been reported following divers and attaching to their legs. They are harmless, but the rough disc can hurt. Don’t try to touch or catch them; watch from a distance.

How big do remoras get?

The common remora is usually about 40 cm long and at most 86.4 cm. The live sharksucker can reach 110 cm, and the marlin sucker only about 40 cm.

Are remoras endangered?

No. The common remora, live sharksucker and whalesucker are listed as Least Concern on the IUCN Red List (assessed in 2012).

Take the discovery with you