Despite their large size and threatening appearance, basking sharks are not aggressive and are harmless to humans.
The basking shark can be found in all the world’s temperate oceans. It prefers 8 to 14.5 °C (46.4 to 58.1 °F) temperatures, but has been confirmed to cross the much-warmer waters at the equator.
The basking shark is often seen close to land, including bays with narrow openings.
The exact lifespan of the basking shark is unknown, but experts estimate to be about 50 years.
Basking sharks typically reach 6–8 meters (20–26 feet) in length and weighs about 5.2 tonnes (5.1 long tons; 5.7 short tons).
Some specimens still surpass 9–10 meters (30–33 feet), but after years of large-scale fishing, specimens of this size have become rare.
The largest accurately measured specimen was trapped in a herring net in the Bay of Fundy, Canada, in 1851. Its total length was 12.27 meters (40.3 feet), and it weighed an estimated 19 tonnes (19 long tons; 21 short tons).
The basking shark has a conical snout, enormous gills, dark bristle-like gill rakers, and a crescent-shaped tail.
The most impressive feature of the basking shark is its mouth, which can be well over 1 meter (3 feet) in width!
Teeth are small and numerous (about one hundred per row) with a single conical cusp usually curved backwards, and similar in both jaws.
Color is grayish brown to black above, often with blotches of a lighter color, and pale with blotches on the belly.
Basking Sharks are one of only three filter-feeding sharks – the others being the whale shark and megamouth shark.
Basking sharks feed on zooplankton – very small fish, and invertebrates.
To capture food, this shark swims with its mouth open widely, gillrakers straining zooplankton from the water.
A shark will typically swim with its mouth open for few minutes, then close its mouth to swallow the filtered plankton before starting the process over again.
The basking shark has to take in a huge amount of water to get enough food; estimates suggest a fairly large basking shark will filter around 1,500,000 litres (400,000 gallons) of water per hour!
Like other sharks, they probably use their sense of smell to find food.
Basking sharks are slow swimmers, going no more than 5 km/h (3 mph).
Though the basking shark is large and slow, it can breach, jumping entirely out of the water. This behaviour could be an attempt to dislodge parasites or commensals.
They are found from the surface down to at least 1,000 meters (3,280 feet).
Although normally solitary, basking sharks are sometimes encountered in small groups, and very occasionally in larger aggregations of 100 individuals or more.
This is a migratory species although its seasonal movements aren’t well known. They dwell in northern waters as long as the plankton population is abundant, moving south in the winter.
Basking sharks are ovoviviparous; its eggs hatch internally and the young are born live when fully developed. Gestation is thought to span over a year (perhaps two to three years), with a small, though unknown, number of young. Only one pregnant female is known to have been caught; she was carrying six unborn young.
The basking shark sheds and regrows its gill rakers in the winter, the only known example of an annual molt in fishes.
This species has the smallest weight-for-weight brain size of any shark, reflecting its relatively passive lifestyle.
The basking shark is listed as vulnerable on the IUCN Red List.
According to the IUCN, basking shark populations are in decline worldwide, and have been for some time.
Aside from direct catches, by-catches in trawl nets have been one of several threats to basking sharks.
The basking shark is tolerant of boats and divers approaching it, and may even circle divers, making it an important draw for dive tourism in areas where it is common.
Historically, the basking shark has been a staple of fisheries because of its slow swimming speed, placid nature, and previously abundant numbers. Commercially, it was put to many uses: the flesh for food and fishmeal, the hide for leather, and its large liver for oil.
Although basking sharks are now a protected species in many countries, they’re still hunted in places like China and Japan for their fins, which are among the most valuable in the shark fin soup trade.
In 2015, a 6.3 meters (21 feet) basking shark was caught by a trawler in seas near Portland, in Southeastern Australia. The whole shark was donated to the Victoria Museum for research, instead of
the fins being sold for use in shark fin soup.
Apart from hunting by humans, killer whales are the only real threat to the basking shark.