The Bluntnose Sixgill Shark (Hexanchus griseus) is a large deep-sea shark belonging to the order Hexanchiformes and the family Hexanchidae. Unlike most modern sharks, which have five gill slits, the Bluntnose Sixgill Shark has six gill slits, making it one of the most primitive living shark species. Having changed very little over hundreds of millions of years, it retains many ancient characteristics and serves as an important apex predator in deep-sea ecosystems.

In this article, we’ll explore the Bluntnose Sixgill Shark’s characteristics, habitat, behavior, diet, reproduction, and ecological importance.

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What Is the Bluntnose Sixgill Shark?

The Bluntnose Sixgill Shark belongs to the order Hexanchiformes and the family Hexanchidae.

Its scientific name is Hexanchus griseus, and it is commonly known as the Bluntnose Sixgill Shark.

The species is widely distributed throughout:

• The Pacific Ocean
• The Atlantic Ocean
• The Indian Ocean
• The Mediterranean Sea
• Temperate and tropical waters around the world

Adult Bluntnose Sixgill Sharks typically measure:

• Body Length: Approximately 3–5 meters (10–16 feet)
• Maximum Length: Up to 5.5 meters (18 feet)
• Weight: Approximately 300–600 kg (660–1,320 lb), with exceptionally large individuals exceeding 700 kg (1,540 lb)

Their estimated average lifespan is about 70–80 years.

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Characteristics of the Bluntnose Sixgill Shark

1. Six Gill Slits

The Bluntnose Sixgill Shark’s most distinctive feature is its six gill slits.

Unlike the vast majority of modern sharks, which possess five gill slits, this species retains an ancient anatomical trait inherited from early shark ancestors.

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2. Massive Body Size

The Bluntnose Sixgill Shark is among the largest deep-sea sharks in the world.

It has a thick, muscular body, a broad head, and a relatively long, asymmetrical tail that provides efficient propulsion through deep waters.

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3. Excellent Deep-Sea Adaptations

This species usually remains in deep water during the day and often migrates into shallower waters at night to hunt.

These daily vertical migrations are a characteristic behavior of many deep-sea predators.

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Behavior

The Bluntnose Sixgill Shark is a nocturnal carnivorous fish.

Its typical behaviors include:

• Remaining in deep water during the day
• Moving into shallower waters at night
• Living primarily a solitary lifestyle
• Swimming slowly but efficiently
• Using an exceptional sense of smell and electroreception to locate prey
• Giving birth to live young through ovoviviparity, in which embryos develop inside eggs that hatch within the mother’s body before birth

Although it generally moves slowly, it is capable of surprising bursts of speed when attacking prey.

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Diet and Habitat

The Bluntnose Sixgill Shark is a carnivorous predator.

Its primary food sources include:

• Bony fishes
• Squid
• Octopuses
• Rays
• Smaller sharks
• Crustaceans
• Whale carcasses (carrion)

Preferred habitats include:

• Continental slopes
• Deep-sea environments
• Submarine canyons
• Areas surrounding underwater seamounts
• Marine depths of approximately 200–2,500 meters (656–8,202 feet)

Although it prefers deep waters rich in prey, it may ascend to depths of only a few dozen meters during nighttime foraging.

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Ecological Importance

The Bluntnose Sixgill Shark is an important apex predator in deep-sea ecosystems.

By feeding on a wide variety of fishes, cephalopods, and other marine animals, it helps regulate prey populations and maintain ecological balance.

It also scavenges whale carcasses and other large marine remains, contributing to nutrient recycling within deep-ocean environments.

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Relationship with Humans

Encounters between humans and the Bluntnose Sixgill Shark are extremely rare.

Because it spends most of its life in deep water, it poses very little risk to people. Nevertheless, due to its enormous size, caution is always advised during rare diving encounters.

The species grows slowly, matures late, and has relatively low reproductive rates, making it vulnerable to overfishing and bycatch. Population declines have been reported in some regions, prompting increased scientific research and conservation efforts.

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The Bluntnose Sixgill Shark is one of the world’s most remarkable deep-sea sharks, distinguished by its six gill slits, enormous size, and ancient evolutionary heritage. Often described as a “living fossil,” it has survived with relatively few changes for hundreds of millions of years while serving as an essential apex predator in the deep ocean.

With continued deep-sea conservation, responsible fisheries management, and ongoing scientific research, the Bluntnose Sixgill Shark will remain an invaluable species for understanding shark evolution and preserving the health of deep-sea ecosystems for generations to come.