About Basking Sharks
Basking Sharks are enormous – they’re the second largest fish in the world! The largest reported Basking Shark was 12 m long, but these days, they are typically less than 10 m. They have been reported as weighing up to 7 tonnes, however the average Basking Shark weighs 4.5 tonnes.
Their mouth can be well over 1 m wide, they have five pairs of gill slits which almost encircle the head, and a powerful crescent-shaped tail. They are grey-brown in colour with a lighter underbelly. Often, they have irregular patches, patterns and streaks on their flanks and fins.
Basking Sharks belong to a group of sharks known as the mackerel sharks. This is a very diverse group, which includes the Goblin Shark, Megamouth Shark, Thresher Shark, Porbeagle, White Shark, Shortfin Mako and Crocodile Shark.
Check out the Basking Shark ID guide entry to find out more.
See our ID guide here for more information on Basking Shark identification and distribution.
Behaviour
Basking Sharks are so called because they're often seen feeding at the surface of the water, basking in the sun! Their snout, large dorsal fin, and caudal (tail) fin can often be seen above the water, making them easily recognisable. Basking Sharks are filter-feeders, which means they eat tiny organisms called plankton. They cruise through the water with their huge mouths open, filtering plankton from the seawater, which gets trapped in their gill-rakers - the long comb-like structures on their gills. The routes that they take, depend on the concentration of plankton as they will follow these trails.
Basking Sharks can be seen on their own, in small groups, or even in schools of hundreds. They often group together with others of the same size or sex.
Despite their size, Basking Sharks can leap 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. Though it has also been suggested that breaching could 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. There are no data on the population size, though genetic results suggest they are one global population.
Range: IUCN; Basemap: World Administrative Boundaries, World Food Programme 2019. (data.opendatasoft.com)
They can travel great distances into the open ocean. While they will usually be at the surface when we encounter them, they have been recorded as deep as 1,264m.
Basking Sharks may venture inshore to shallow bays, almost to the surf line. And can be seen from land at certain times of the year. They seem to favour headlands, islands, and bays with strong tidal flow – this tends to be where different water bodies meet and there will be an abundance of plankton.
Basking Sharks are rarely seen at the surface in the winter months, and it was previously suggested that they might hibernate. But now, thanks to satellite tagging, we know that they spend their winter months in deeper water, feeding on deep-water plankton.
In British waters, Basking Sharks are often spotted between around March and October. But despite this, there is still more to learn about the largest shark in these waters!
Reproduction
It's thought that Basking Sharks live for at least 50 years with males reach maturity at 12–16 years and females at 16-20 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 in length. This means Basking Shark pups are larger at birth than many species of shark are fully grown!
Gestation is estimated at being between 12 – 36 months and they likely have a resting period of two years between litters. There's only ever been one reported catch of a pregnant female (1943), who was carrying six pups.
