# Basking Shark — Facts, Threats & Conservation

*Cetorhinus maximus (Gunnerus, 1765) — family Cetorhinidae*

> 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.

**IUCN status:** Endangered — the second-largest fish, and harmless  ·  **WARN range:** Temperate coastal waters worldwide, Summer surface feeding off Britain, Ireland and the north-east Atlantic

## Quick facts
| Fact | Value |
| --- | --- |
| 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
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Chondrichthyes
- **Order:** Lamniformes
- **Family:** Cetorhinidae
- **Genus:** Cetorhinus
- **Species:** Cetorhinus maximus

## Conservation status
- **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.

## 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.

## Frequently asked questions: Basking Shark
### 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
- [IUCN Red List — Cetorhinus maximus](https://www.iucnredlist.org/species/4292/166822294)
- [CITES Appendices](https://cites.org/eng/app/appendices.php)

---
Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/basking-shark