Animal
Megamouth shark
The megamouth shark is a big, gentle shark with a giant mouth. It eats tiny shrimp called krill. People have seen it only a few times.
The megamouth shark is a huge, slow shark with a big, rounded head and an enormous mouth. It swims with its mouth open to gulp tiny shrimp called krill and other small animals. It lives far out in the open ocean and is so rarely seen that scientists did not know it existed until 1976.
Megachasma pelagios is a large, soft-bodied filter-feeding shark of the open ocean, placed in a family of its own, first discovered off Hawaii in 1976. It appears to migrate up and down each day following krill. The IUCN knew of just over 120 documented specimens as of December 2018 and lists it as Least Concern, while warning that rising bycatch, especially off Taiwan, needs careful tracking.
Photo: Oos, CC BY-SA 3.0, via Wikimedia Commons
Meet the megamouth shark
The megamouth shark is a very big shark with a very big mouth.
It is dark on top and pale underneath. It is gentle and swims slowly. It eats tiny shrimp, not big animals.
The megamouth shark is a giant of the open ocean. It has a big, soft, rounded head, a huge mouth right at the front, and a soft, flabby body. Its back is dark gray, bluish black or brownish, and its belly is pale. Along the front of its snout runs a white band.
The inside of its mouth is silvery, and its jaws hold many rows of tiny hooked teeth. But the megamouth does not hunt big animals. It is a filter feeder that eats krill, small shrimp-like animals, and other tiny creatures.
Megachasma pelagios is a cartilaginous fish (class Chondrichthyes, order Lamniformes) placed in its own family, Megachasmidae: a new family, genus and species had to be created for it, and it was formally described in 1983. The Florida Museum describes a stout body with a bulbous head, a broad terminal mouth extending behind the eyes, low dorsal fins and an asymmetrical tail; its soft, poorly calcified skeleton, loose skin and soft fins probably make it a poor swimmer.
It is one of three filter-feeding sharks, with the whale shark and the basking shark, and studies suggest that its filter feeding evolved separately from the basking shark's.
Quick facts
- Group
- Fish
- Length
- 4.46 to 5.15 m
A mystery of the open ocean
Megamouth sharks live far out in the ocean.
They swim in warm seas around the world. They are very hard to find.
Megamouth sharks live in the open ocean, in warm and mild seas around the world, in the Pacific, Indian and Atlantic Oceans. Far more have been found near Taiwan, Japan and the Philippines than anywhere else.
They have been recorded from just 5 meters below the surface down to about 1,500 meters deep. Because they live so far from shore and so deep, nobody knows exactly where all of them live.
The IUCN describes the megamouth as wide-ranging in tropical and temperate parts of all major oceans, though its full distribution is poorly known, with considerably more specimens from Taiwan, Japan and the Philippines than elsewhere. Countries with records include Australia, Brazil, China, Ecuador, Indonesia, Japan, Mexico, Peru, the Philippines, Puerto Rico, Senegal, South Africa, Sri Lanka, Taiwan, the United States and Viet Nam.
It occurs over the continental shelf and in oceanic waters, recorded as shallow as 5 meters near the coast and offshore at 8 to 1,500 meters over water 348 to 4,600 meters deep. Genetic samples from Taiwan and California showed no genetic diversity, suggesting a single, highly migratory population (Florida Museum, citing Liu and colleagues, 2018).
Its habitat
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Open ocean and continental-shelf waters of tropical and temperate seas worldwide, from near the surface to about 1,500 m. Most records come from Taiwan, Japan and the Philippines; the full range is poorly known. Shading is by whole ocean.
Places: Atlantic Ocean, Indian Ocean and Pacific Ocean.
Source: iucn-red-list · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in Japan, Philippines, United States, Mexico, Taiwan, Australia, South Africa, Brazil and 7 more places.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
A filter-feeding giant
Megamouth sharks eat krill.
Krill are tiny animals that look like shrimp. The shark swims with its mouth wide open to catch lots of them.
The megamouth is a filter feeder. Scientists think it swims slowly through swarms of krill, small shrimp-like animals, with its huge mouth open, sucks them in, then closes its mouth and pushes the water out through its gills, keeping the food.
Every megamouth studied had krill in its stomach. Some had also eaten tiny copepods and jellyfish.
Precise feeding behavior has not been observed, but the Florida Museum summarizes the accepted model: the shark swims slowly through aggregations of euphausiid shrimp (krill) with its mouth open, protrudes its jaws and expands its mouth cavity to suck prey in, then closes the mouth and expels water through the gill openings. All specimens analyzed contained euphausiids; the second also held copepods and the jellyfish Atolla vanhoeffeni.
The Australian Museum lists shrimps, copepods and pelagic jellyfish in the diet. The Florida Museum notes a hypothesis that the white band on the snout might help attract prey.
Did you know?
Surfers once tried to help a megamouth back to the sea.
In 1988 in Western Australia, surfers thought a megamouth was a whale and tried to guide it into deeper water.
The day before a 5.15 m male stranded at Mandurah, Western Australia, in August 1988, surfers who mistook it for a whale tried to coax it to deeper water (Australian Museum).
A soft giant with a huge mouth
The megamouth has a huge, rounded head and a giant mouth.
Its body is soft. It has a white stripe on the front of its snout.
The megamouth's mouth opens right at the front of its big, rounded head and reaches back behind its eyes. Inside, its jaws hold about 50 rows of tiny teeth, though only three rows are used.
Its body is soft and flabby, with soft fins, a lopsided tail with a strong lower part, and a skeleton that is not very hard. This makes it light in the water but a slow swimmer. Most of its fins have white tips.
The head is bulbous with a broadly rounded snout; the broad terminal mouth extends behind the eyes, its interior is silvery, and each jaw carries about 50 rows of small, hooked teeth, of which only three are functional (Florida Museum, Australian Museum). The gill slits are moderately long, the pectoral fins shorter than the head in adults, and the second dorsal fin less than half the size of the first.
Unlike many sharks that rely on a large oily liver to stay buoyant, the megamouth reduces its density with a soft, poorly calcified skeleton, very loose skin and loose connective tissue and muscle. A white band on the front of the snout contrasts with the dark head; scientists have suggested it may attract prey or help megamouths recognize each other.
Still largely a mystery
Scientists still have a lot to learn about baby megamouths.
They think the babies grow inside their mother before they are born.
Nobody has ever seen a baby megamouth being born. Scientists think the babies hatch from eggs inside their mother and grow there before birth, as in their relatives, the mackerel sharks. The Florida Museum describes only one known grown-up female, and her body held many eggs.
The smallest megamouth ever found was 1.77 meters long, but nobody knows if that is close to the size at birth. Males are thought to be grown up by about 4 to 5.5 meters.
Reproduction is probably aplacental (lecithotrophic) viviparity with uterine cannibalism or oophagy, as in other lamniform sharks (IUCN, citing Ebert and colleagues 2013). The only known mature female described by the Florida Museum was 5.44 meters long, with a right ovary holding many eggs.
The smallest known specimen measured 177 centimeters, and whether that is near birth size is unknown (IUCN). Males are known to be mature by 4 meters (Australian Museum); the Florida Museum gives probable maturity at 4.5 to 5.5 meters for males and 5 meters for females. Two mature males caught off southern California in late October and November showed signs of recent mating, suggesting the area may be a fall mating ground.
Up at night, down by day
At night the megamouth swims up near the surface.
In the daytime it swims down into deep, dark water. It follows the krill it eats.
Scientists once caught a live megamouth near Los Angeles, tagged it and followed it for about two days. At night it stayed near the surface, about 12 to 25 meters down. At dawn it dove to about 120 to 170 meters, and at dusk it rose again.
The krill it eats make the same daily trip, so scientists think the megamouth follows its food up and down. It is a slow swimmer.
The sixth specimen, caught off Dana Point near Los Angeles, was fitted with an ultrasonic transmitter and tracked for about 50 hours: it spent daylight hours at about 120 to 170 meters and moved up to about 12 to 25 meters at dusk, remaining shallow through the night (Australian Museum, Florida Museum). This diel vertical migration matches that of its euphausiid prey.
Most specimens show crater-shaped scars from cookiecutter sharks. The only confirmed predation event involved sperm whales off North Sulawesi, Indonesia, in August 1998 (Florida Museum).
Did you know?
Megamouth means 'big mouth'.
The scientific name Megachasma comes from Greek words meaning 'great' and 'cave', for its huge mouth.
Megachasma derives from Greek megas (great) and chasma (cave), and pelagios means 'of the sea' (Florida Museum).
Rare, and worth watching
Megamouth sharks are very rare to see.
Sometimes they get caught by mistake in fishing nets. Scientists keep track of every one that is found.
The megamouth is listed as Least Concern by the IUCN, because it lives across a huge area and is rarely caught. But nobody knows how many there are, and more are now being caught by accident in fishing nets, especially near Taiwan.
Scientists keep a list of every megamouth ever found. In the United States, fishers in the Pacific have not been allowed to keep megamouths since 2004, except to give or sell them for science or display, and in Taiwan every catch must be reported.
The IUCN's 2018 assessment (published 2019) lists the megamouth as Least Concern because of its wide range and generally limited contact with fisheries, but notes that its rarity, intrinsic sensitivity to overexploitation and increasing capture in Asia mean catches must be tracked. Off eastern Taiwan, 34 megamouths were recorded as bycatch in a driftnet fishery for sharptail mola between April 2013 and May 2015.
Retention has been prohibited in US Pacific fisheries since 2004 (refined in 2015 to allow donation or sale for research, education or display), and Taiwan requires catches to be reported. The IUCN recommends live release and a seasonal closure of the Taiwanese driftnet fishery from April to August.
IUCN Red List
How is the megamouth shark doing in the wild?
- Least Concern (this animal)
- Near Threatened
- Vulnerable
- Endangered
- Critically Endangered
- Extinct in the Wild
- Extinct
Least Concern
Not at risk of disappearing from the wild right now.
See the IUCN Red List assessment · The IUCN Red List of Threatened Species 2022.2
Amazing facts
-
The first megamouth got tangled in a ship's sea anchor.
The first megamouth ever found, in 1976, was caught in a parachute used as a sea anchor by a research ship off Hawaii.
On 15 November 1976 a 4.46 m male was found entangled in a parachute sea anchor deployed at about 165 m off Kaneohe, Hawaii (Australian Museum).
-
Surfers once tried to help a megamouth back to the sea.
In 1988 in Western Australia, surfers thought a megamouth was a whale and tried to guide it into deeper water.
The day before a 5.15 m male stranded at Mandurah, Western Australia, in August 1988, surfers who mistook it for a whale tried to coax it to deeper water (Australian Museum).
-
Megamouth means 'big mouth'.
The scientific name Megachasma comes from Greek words meaning 'great' and 'cave', for its huge mouth.
Megachasma derives from Greek megas (great) and chasma (cave), and pelagios means 'of the sea' (Florida Museum).
-
It is one of only three sharks that eat by filtering tiny food.
The megamouth is one of three filter-feeding sharks, along with the whale shark and the basking shark.
Along with the whale and basking sharks it is one of three filter-feeding sharks, but its filter feeding appears to have evolved independently of the basking shark's.
Words to know
- filter feeder
- an animal that strains tiny food out of the water
- krill
- small, shrimp-like ocean animals that many larger animals eat
- bycatch
- animals caught by accident while fishing for something else
- specimen
- one animal that scientists collect or study
- vertical migration
- moving up and down in the water each day
- gill slits
- openings on a shark's side where water flows out over the gills
Discovery challenge
-
What does the megamouth eat?
What is the megamouth shark's main food?
Which prey dominates the megamouth's diet?
- Tiny krill
- Big whales
- Seaweed only
Show the answer
Tiny krill
It eats tiny shrimp-like animals called krill.
It is a filter feeder that eats krill, plus copepods and jellyfish.
Euphausiid shrimp (krill); every specimen analyzed contained them.
-
When was the first megamouth found?
In which year was the first megamouth shark found?
When was the first megamouth specimen recovered?
- 1776
- 1976
- 2016
Show the answer
1976
The first one was found in 1976.
It was found in 1976 off Hawaii, caught in a ship's sea anchor.
On 15 November 1976 off Kaneohe, Hawaii; the species was described in 1983.
-
Where is the megamouth at night?
Where did the tracked megamouth swim at night?
Where did the tracked megamouth spend its nights?
- Near the surface
- On the beach
- In a river
Show the answer
Near the surface
It swims up near the top of the sea at night.
At night it stayed only 12 to 25 meters down, then dove deeper in the day.
Shallow (12 to 25 m) at night and deeper (120 to 170 m) by day: diel vertical migration.
-
Is the megamouth seen often?
How often have people found megamouth sharks?
How often had megamouths been documented by December 2018, according to the IUCN?
- Hardly ever: just over 120 by December 2018
- Every day at the beach
- Millions every year
Show the answer
Hardly ever: just over 120 by December 2018
Hardly ever! Only a small number have been found.
Very rarely: scientists had documented just over 120 by December 2018.
Just over 120 documented specimens as of December 2018, most from Taiwan, Japan and the Philippines.
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For parents & teachers
What children will learn
- Describe how the megamouth shark feeds as a filter feeder.
- Explain diel vertical migration using the tracked megamouth as an example.
- Understand how scientists study a species known from very few records, and why counts carry dates.
Recommended ages: 3 to 17 · About 10 minutes
Talk about it
- How could a shark over 4 meters long stay undiscovered until 1976?
- Why might an animal follow its food up and down every day?
- Why is it important for fishers to report rare animals they catch by accident?
Try at home or in class
- Use a kitchen sieve to scoop rice or small pasta out of a bowl of water, the way a filter feeder keeps food and lets water go.
- Measure 5 meters on the floor with a tape measure to see how long the first megamouths were.
Key vocabulary: filter feeder, krill, bycatch, specimen, vertical migration, gill slits
Where these facts come from
- The IUCN Red List of Threatened Species , International Union for Conservation of Nature (IUCN terms of use (no redistribution of Red List data or range maps))
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Megachasma pelagios (Megamouth Shark), 2019 global assessment , IUCN Red List of Threatened Species
- Megamouth Shark, Megachasma pelagios , Australian Museum
- Megamouth shark species profile , Florida Museum of Natural History
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 27, 2026. Spotted a mistake? Tell us.