See our ID guide here for more information on Basking Shark identification and distribution.

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APPEARANCE

Basking Sharks are enormous – they are the 2^nd biggest fish in the world! The largest reported Basking Shark was 12 m long and the average Basking Shark weighs 4.5 tonnes. However, they can weigh up to 7 tonnes!

They have a very large mouth (this can be well over 1 m wide!), 5 huge gills which almost encircle the head and a powerful crescent-shaped tail. They tend to be greyish-brown with a lighter underbelly. Often they have irregular patches, patterns and streaks on their flanks and fins. Using photo-ID we can use these distinct markings on their fins to identify individual Basking Sharks. To learn more see the Basking Shark Project page

They belong to a group of sharks known as the mackerel sharks. A very diverse group, which includes the Goblin, Megamouth, Thresher, Porbeagle, White, Shortfin Mako and Crocodile Shark – many of which can be found in UK waters.

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Behaviour

Basking Sharks are so named because they're often seen feeding at the surface of the water - where they look like they're basking in the sun! Basking Sharks are filter-feeders, and can detect different concentrations of plankton in the water, guiding them to the best feeding grounds. They swim through the water with their mouth wide open, scooping up any plankton in the water trapping it in the long comb-like structures on their gills (known as gill-rakers).

Basking Sharks are quite social. They can be seen on their own, in small groups, or schools of hundreds. There are many reports of same size and sex groups. Suggesting a strong sexual and age segregation within the species.

Despite their size, Basking Sharks are capable of leaping clear out of the water. A behaviour known as breaching. They seem to breach most when in large groups and during courtship, so this may act as a social or sexual function. It could also help to dislodge external parasites.

Distribution

Basking Sharks are found around the world in warm-temperate waters, and in deeper cooler waters in the tropics:

Range: IUCN; Basemap: World Administrative Boundaries, World Food Programme 2019. (data.opendatasoft.com)

This coastal species can travel great distances into the open ocean. While we usually encounter them near the surface, they have been recorded as deep as 1264m.

Basking Sharks may venture inshore to shallow bays, almost to the surf line. And are often seen from land at certain times of the year. They seem to prefer headlands, islands, and bays with strong tidal flow. Where different masses of water meet and there is an abundance of plankton.

Basking Sharks are rarely seen at the surface in the winter months, and it was once suggested that they might hibernate. But now, thanks to satellite tagging, we know that they spend their time in deeper water, feeding on deep-water plankton.

In British waters Basking Sharks are often spotted between May and October. But despite this, there is still more to learn about the largest shark in UK waters!

Reproduction

It's thought that Basking Sharks live for at least 50 years. Males reach maturity at 12–16 years. And females at 20 years (around 4.5-6 m in length).

Females produce eggs, which develop and hatch inside their body (this is known as ovoviviparity). They then give birth to fully developed young, which are around 1–2 m long. This makes Basking Shark pups larger at birth than many species of shark are fully grown!

There is still more for us to learn about Basking Shark reproduction. Pregnancy is thought to last around 14 months - there's only ever been one reported catch of a pregnant female (1943), who was carrying six pups.