American Oceans

Bluntnose Sixgill Shark

The Bluntnose sixgill shark, also known as Hexanchus griseus, is a fascinating species of shark that inhabits the deep waters of the world’s oceans.

a close up of a rare sixgill shark

It is one of the largest predatory sharks, growing up to 20 feet in length and weighing over 1,000 pounds.

This shark species has a unique appearance with a broad head, six gill slits, and a long tail.

Despite its impressive size and predatory nature, the Bluntnose sixgill shark is not considered a significant threat to humans.

However, like many other shark species, it is vulnerable to overfishing and habitat destruction.

As a result, conservation efforts are underway to protect this species and ensure its survival for future generations.

Physical Characteristics

the face of a sixgill shark up close

Bluntnose sixgill sharks are large, slow-moving predators that can grow up to 5 meters (16.5 feet) in length and weigh up to 1000 kg (2200 pounds).

They have a unique body structure that distinguishes them from other shark species.

Body Structure

The body of the bluntnose sixgill shark is long and cylindrical, with a broad and flattened head.

The lower jaw is longer than the upper jaw, and both jaws are lined with sharp, serrated teeth.

The skin of the shark is rough and covered in tiny scales called dermal denticles, which help to reduce drag as the shark moves through the water.

Eyes and Snout

The bluntnose sixgill shark has large, round eyes that are positioned on the sides of the head.

This allows the shark to have a wide field of vision, which is useful for detecting prey. The snout of the shark is broad and rounded, with a slightly protruding lower jaw.

Gill Slits

The bluntnose sixgill shark has six gill slits on either side of its body. This is a distinguishing characteristic that sets it apart from other shark species, which typically have five gill slits.

Fins and Tail

The bluntnose sixgill shark has two dorsal fins, one large and one small, and a long, pointed caudal fin.

The pectoral fins are large and broad, while the pelvic fins are small and positioned towards the rear of the body.

The shark’s fins are used for balance, maneuverability, and propulsion through the water.

Distribution and Habitat

a sixgill shark swimming underwater

The bluntnose sixgill shark (Hexanchus griseus) is a cosmopolitan species with a wide distribution range throughout the world’s temperate and tropical waters.

They can be found in the Atlantic, Indian, and Pacific oceans, as well as the Mediterranean Sea.

They are known to inhabit deep water, with a depth range of up to 500 meters.

Habitat Preferences

Bluntnose sixgill sharks prefer to inhabit the continental shelf and the upper slope, but they can also be found in coastal areas.

They tend to be more active at night and are known to feed on a variety of prey, including bony fish, squid, and other sharks.

The depth distribution of sixgill sharks suggests that they prefer hypoxic water during the day, but their behavior and habitat preferences are not yet fully understood.

In Hawaii, bluntnose sixgill sharks have been observed in the water column near the bottom, at depths ranging from 200 to 400 meters.

In the eastern north Sicilian waters, they are known to have an important influence on the Mediterranean marine food chain due to their wide prey spectrum and almost no natural predators.

Diet and Feeding Behavior

the face of a sixgill shark

Bluntnose sixgill sharks are large-bodied marine predators that exhibit a wide range of dietary preferences and feeding strategies.

This section will explore the dietary and feeding behavior of these sharks in detail.

Dietary Preferences

Bluntnose sixgill sharks are opportunistic feeders and have a diverse diet that varies depending on the availability of prey items in their habitat.

Studies have shown that they tend towards generalist feeding behavior, consuming a wide range of prey items from different trophic levels.

They are known to feed on a variety of fish, squid, crustaceans, and even other sharks.

The diet of bluntnose sixgill sharks can vary depending on their life stage.

Juvenile sharks tend to feed on smaller prey items such as squid and small fish, while adult sharks prefer larger prey items such as dogfish and other sharks.

Feeding Strategies

Bluntnose sixgill sharks have a variety of feeding strategies that they use to capture their prey.

They are known to be nocturnal feeders and are most active during the night. They have been observed using a variety of hunting techniques such as ambush, pursuit, and scavenging.

One of the primary feeding strategies used by bluntnose sixgill sharks is ambush hunting. They are known to use their large size and stealthy approach to surprise their prey and capture it quickly.

They also use their strong jaws and sharp teeth to tear apart their prey and consume it.

Another feeding strategy used by bluntnose sixgill sharks is scavenging.

They are known to feed on carrion and are often found scavenging on the remains of dead animals on the ocean floor.

Reproduction and Lifespan

Bluntnose sixgill sharks are ovoviviparous, meaning that the embryos develop inside eggs within the female’s body until they hatch and are born as live young.

The breeding patterns of bluntnose sixgill sharks are not well understood, but it is believed that they have a low reproductive rate due to their slow growth and late reproductive maturity, which occurs at approximately 20 years of age.

Additionally, the sex ratio of the species appears to be in favor of females, which may further limit their breeding potential.

Gestation and Pups

Gestation periods for bluntnose sixgill sharks are estimated to be between 12 and 24 months, with females giving birth to litters of 22-108 pups.

The size of the litter is dependent on the size of the female, with larger females producing larger litters.

The pups are born measuring between 60 and 75 cm in length and are immediately independent, with no parental care provided after birth.


Bluntnose sixgill sharks are known for their longevity, with estimates suggesting that they can live up to 80 years.

The slow growth and late reproductive maturity of the species contribute to their extended lifespan.

However, due to their low reproductive rate and vulnerability to overfishing, bluntnose sixgill sharks are listed as a vulnerable species by the International Union for Conservation of Nature (IUCN).

Conservation Status and Threats

The bluntnose sixgill shark (Hexanchus griseus) is listed as “Data Deficient” on the International Union for Conservation of Nature (IUCN) Red List.

This means that there is insufficient information to assess the species’ conservation status. However, the species is listed as “Endangered” under Canada’s Species at Risk Act.


The bluntnose sixgill shark faces several threats, including overfishing, bycatch, and habitat degradation.

The species is often caught as bycatch in commercial and recreational fisheries targeting other species. The sharks are also vulnerable to entanglement in fishing gear, which can lead to injury or death.

Humans are also a threat to bluntnose sixgill sharks. The species is sometimes hunted for its meat, liver oil, and fins, which are used in traditional Chinese medicine.

Additionally, the sharks’ slow growth and low reproductive rate make them particularly vulnerable to overfishing.

Predators of the bluntnose sixgill shark include killer whales and other large predatory sharks. In shallow waters, the species may also be preyed upon by larger fish and marine mammals.

Efforts are underway to conserve the bluntnose sixgill shark. These include measures to reduce bycatch, such as the use of modified fishing gear and time-area closures.

Additionally, marine protected areas have been established to protect the species’ habitat. Ongoing research is also helping to improve our understanding of the species’ biology and ecology, which will aid in conservation efforts.

Scientific Classification and Related Species

The Bluntnose Sixgill Shark, scientifically known as Hexanchus griseus, belongs to the family Hexanchidae of the order Hexanchiformes.

This order includes the sixgill sharks, cow sharks, and frilled sharks. The Bluntnose Sixgill Shark is the largest and most common of the sixgill sharks. It is also known as the Atlantic Sixgill Shark or Bigeyed Sixgill Shark.

The scientific classification of the Bluntnose Sixgill Shark is as follows:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Chondrichthyes
  • Order: Hexanchiformes
  • Family: Hexanchidae
  • Genus: Hexanchus
  • Species: Hexanchus griseus

Related Species

The Bluntnose Sixgill Shark is closely related to other members of the Hexanchidae family, including the Greenland Shark (Somniosus microcephalus) and the Bigeyed Sixgill Shark (Hexanchus nakamurai).

These sharks are characterized by their six or seven gill slits, compared to the five found in most other sharks.

The Bluntnose Sixgill Shark is also related to the Chlamydoselachus anguineus, commonly known as the Frilled Shark.

This species is also a member of the Hexanchiformes order, but belongs to a different family, the Chlamydoselachidae.

Interaction with Humans

The bluntnose sixgill shark has a long history of interaction with humans, both in research and popular culture.

In Research

Researchers have studied the bluntnose sixgill shark extensively in recent years, particularly in areas such as Puget Sound and the waters around Hawaii.

These studies have shed light on the shark’s behavior, habitat, and biology, as well as its interactions with other marine species.

One notable study conducted by researchers at the Florida Museum of Natural History examined catch rates and biological characteristics of bluntnose sixgill sharks in Puget Sound.

The study found that the shark’s population had declined significantly in the area, likely due to overfishing and other human activities.

In Popular Culture

The bluntnose sixgill shark has also been a popular subject in popular culture, appearing in films, television shows, and other media.

One notable example is the 1977 film “The Deep,” which features a bluntnose sixgill shark attacking the film’s protagonists.

Despite its frequent appearances in popular culture, the bluntnose sixgill shark remains a relatively unknown species to many people.

However, increased research and conservation efforts may help to raise awareness of this fascinating and important animal.

Unique Features

The bluntnose sixgill shark (Hexanchus griseus) is a large, apex predator that is widely distributed but poorly understood.

It possesses several unique features that set it apart from other shark species.

Teeth and Jaw

One of the most distinctive features of the bluntnose sixgill shark is its saw-like teeth. The shark has six rows of teeth in its upper jaw and a single row in its lower jaw.

The teeth are triangular in shape and have serrated edges, which make them effective at tearing through tough prey.

The shark’s upper jaw is also unique in that it is not fused to the skull, allowing it to move independently.

This flexibility allows the shark to open its mouth wider than other shark species, making it easier to swallow larger prey.

Lateral Line

The bluntnose sixgill shark also has a well-developed lateral line system. This system is a series of sensory organs that run along the shark’s body and allow it to detect changes in water pressure and movement.

This helps the shark to locate prey, even in low light conditions.

Neural Arches

The shark’s neural arches are another unique feature. These arches are bony structures that protect the spinal cord. In the bluntnose sixgill shark, the neural arches are larger and more robust than in other shark species.

This may be an adaptation to the shark’s deep-sea environment, where the pressure is much greater than at the ocean surface.

Frequently Asked Questions

What is the average size of a bluntnose sixgill shark?

Bluntnose sixgill sharks are large, deep-sea sharks that can grow up to 16 feet (4.9 meters) in length. The average size of a bluntnose sixgill shark is around 10-12 feet (3-3.7 meters) long.

How deep can bluntnose sixgill sharks dive?

Bluntnose sixgill sharks are known to dive to depths of up to 8,200 feet (2,500 meters), making them one of the deepest-diving sharks in the world.

What do bluntnose sixgill sharks eat?

Bluntnose sixgill sharks are opportunistic predators that feed on a variety of prey, including fish, squid, octopus, and even other sharks. They are known to scavenge on carrion as well.

How long can bluntnose sixgill sharks live?

Bluntnose sixgill sharks have a relatively slow growth rate and a long lifespan, with some individuals living up to 80 years or more.

What are some common predators of bluntnose sixgill sharks?

Bluntnose sixgill sharks are apex predators and have few natural predators. However, they may occasionally be preyed upon by larger sharks, killer whales, and possibly other large marine animals.

What is the conservation status of bluntnose sixgill sharks?

Bluntnose sixgill sharks are classified as “Data Deficient” by the International Union for Conservation of Nature (IUCN), meaning that there is not enough data available to assess their conservation status.

However, they are known to be vulnerable to overfishing and habitat destruction, and are listed as a “Species of Concern” by the National Marine Fisheries Service in the United States.

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