Wildlife Guide · Temperate coastal waters worldwide & Summer surface feeding off Britain, Ireland and the north-east Atlantic

Basking Shark

Cetorhinus maximus (Gunnerus, 1765) — family Cetorhinidae

The second-largest fish on Earth, filtering an Olympic pool of water every couple of hours.

Endangered — the second-largest fish, and harmless

Basking shark with enormous open mouth filter-feeding near the surface

Image: AI-generated educational wildlife portrait — World Animal Rescue Network · AI visualisation, not a photograph

In brief

The basking shark (Cetorhinus maximus) is the second-largest fish on Earth at around 10 metres, an entirely harmless filter feeder that strains plankton at the surface, and is listed as Endangered.

By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated July 2026

The basking shark is the second-largest fish alive, reaching around 10 metres, and it feeds by swimming slowly at the surface with its mouth open, straining plankton through enormous gill rakers. The name comes from that habit — it appears to be basking in the sun. It is entirely harmless. Its teeth are tiny and unused, and it has no interest in anything larger than a copepod. Despite that, the species was hunted heavily for liver oil and remains Endangered, recovering slowly from a century of exploitation.

~10 m

Maximum length — second only to the whale shark

Passive

Filters by swimming; no active suction, unlike whale sharks

~1 m

Mouth width when feeding

18 yr

Approximate age at maturity

Figures sourced from IUCN Red List — Cetorhinus maximus, CITES Appendices .

Basking Shark: Quick Facts

Vital statistics and key facts about the Basking Shark
Maximum length	~10 m
Feeding	Passive filtering — requires forward motion
Diet	Zooplankton, principally copepods
Age at maturity	Around 18 years
Historic use	Hunted for liver oil
Trade status	CITES Appendix II

Scientific Classification

Scientific classification of the Basking Shark
Kingdom	Animalia
Phylum	Chordata
Class	Chondrichthyes
Order	Lamniformes
Family	Cetorhinidae
Genus	Cetorhinus
Species	Cetorhinus maximus

Conservation Status

IUCN Status: Endangered
Population: Unknown; north-east Atlantic populations severely reduced by historic fishing
Trend: Decreasing
Assessed: 2018
CITES: Appendix II

Surface feeding makes them unusually vulnerable to vessel strikes. Protection requires international coordination because individuals cross ocean basins.

Did you know?

Basking sharks were once thought to hibernate on the seabed through winter; satellite tags showed they simply move deeper and keep feeding.

Key Facts: Basking Shark

Basking sharks are the second-largest fish, after whale sharks.
They filter passively, relying on forward motion rather than suction.
They are completely harmless, with tiny unused teeth.
Liver oil hunting removed large numbers through the twentieth century.
They are Endangered and recover slowly, maturing at around 18 years.

Passive filtering

A basking shark cruises with its mouth wide open, water passing over gill rakers that comb out plankton before it exits through the gill slits. Unlike whale sharks, which can hold station and actively suction, basking sharks rely entirely on forward motion, which is why they are so often seen moving slowly at the surface. The rakers are shed and regrown, and feeding is seasonal: basking sharks track plankton blooms, appearing predictably in some coastal waters through summer and largely disappearing in winter.

Where they go in winter

Their winter movements were a long-standing mystery, and it was once proposed that they hibernated on the seabed. Satellite tagging resolved it: basking sharks move to deeper water and continue feeding at depth, and some undertake long migrations, including transatlantic crossings. This matters for protection, because a species that crosses ocean basins cannot be safeguarded by one country's rules alone.

A century of liver oil

Basking sharks were hunted intensively for the oil in their enormous livers, used for lamp fuel, lubricants and industrial processes. Fisheries in the north-east Atlantic took very large numbers, and local populations collapsed and in some cases have still not recovered. Because the species matures at around 18 years and produces few young, recovery is measured in decades. Protection is now widespread across their range, and the species is CITES Appendix II listed.

Modern pressures

Direct hunting is largely over, but basking sharks are still killed as bycatch in nets, struck by vessels while feeding at the surface, and disturbed at aggregation sites by boat traffic. Surface feeding is the vulnerability: an animal that spends hours moving slowly just below the waterline is exactly the animal a boat is most likely to hit. Speed restrictions and approach rules at known feeding sites are the practical protection.

What WARN Does

WARN publishes free, sourced species education for animals whose recovery depends on decisions taken far from where the public sees them. Basking sharks cross ocean basins, so their protection depends on coordination between countries — and on boat operators observing approach limits at summer feeding sites.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

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How can I help save the basking shark?

There are three practical things that make a real difference for the basking shark — and the first is the one that funds everything else.

Fund frontline rescue

Back the partner-led teams, veterinary care and protection that reach basking sharks where the need is greatest — WARN channels donations straight to that work.

Ease the pressures

Avoid the wildlife trade and souvenirs, never buy wild animals as pets, and choose sustainable, habitat-friendly products — the threats behind the basking shark's decline fall when demand does.

Spread the word

Share accurate, sourced information about the basking shark. Wider awareness is what turns concern into lasting protection.

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Basking Shark: Frequently Asked Questions

How can I help save the basking shark?

The most effective way to help the basking shark is to fund the frontline rescue and habitat protection that keeps the species alive — WARN channels donations to partner-led teams working where the need is greatest. You can also ease the pressures behind its decline by avoiding the wildlife trade and souvenirs, never buying wild animals as pets, and choosing sustainable products, and by sharing accurate information to build wider support. See the ways to help below, or support WARN's Support Habitat Protection.

Are basking sharks dangerous?

No, not at all. They are filter feeders with tiny, unused teeth that eat plankton. The only realistic risk is accidental contact with a very large animal, which is why approach distances exist at feeding sites.

How big do basking sharks get?

Around 10 metres, making them the second-largest fish alive after the whale shark. Their mouths can open to roughly a metre wide when feeding.

Do basking sharks hibernate in winter?

No — that was a long-standing hypothesis, disproved by satellite tagging. They move into deeper water and continue feeding, and some individuals undertake long migrations including transatlantic crossings.

Why were basking sharks hunted?

For the oil in their very large livers, used as lamp fuel, lubricant and in industrial processes. North-east Atlantic fisheries took large numbers through the twentieth century, and some local populations have still not recovered.

Are basking sharks endangered?

Yes, the IUCN lists them as Endangered. They mature at around 18 years and produce few young, so recovery from historic hunting is measured in decades, and bycatch and vessel strikes continue to remove animals.

What do basking sharks eat?

Basking Sharks eat Zooplankton, principally copepods. The basking shark (Cetorhinus maximus) is the second-largest fish on Earth at around 10 metres, an entirely harmless filter feeder that strains plankton at the surface, and is listed as Endangered.

Where do basking sharks live?

Basking sharks occur in temperate coastal waters worldwide, feeding at the surface in summer off Britain, Ireland and the north-east Atlantic. They were hunted heavily for liver oil through the twentieth century and remain Endangered, recovering slowly from a century of exploitation.

How long do basking sharks live?

Basking sharks mature at around 18 years according to this guide's quickFacts and stats. That slow life history, combined with passive surface filtering that requires forward motion, means recovery from historic hunting is measured in decades rather than years.

Sources & References

Population figures, conservation status and biological facts on this page are drawn from authoritative scientific and intergovernmental sources.

Terms used on this page

Plain-English definitions, from our wildlife and conservation glossary.

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