Basking Shark

Basking sharks, also known as bone sharks, may have an intimidating appearance and massive size that could easily frighten nearby swimmers or divers, but they are essentially harmless as far as humans and aquatic animals are concerned. Much like whales, these sharks feed on plankton and other tiny life forms by filtering vast amounts of ocean water through their mouths. They routinely cruise or even float along the surface with their mouths hanging open as they gather food. They are the second-largest living fish on Earth (after the whale shark) and one of only three sharks that rely on plankton as a food source.

5 Incredible Basking Shark Facts!

• Filtration experts: Their massive size and large mouths allow these sharks to filter thousands of gallons of water per hour.
• Mouth agape: These sharks tend to swim with their big mouth hanging wide open, which can be intimidating to divers who don’t know better.
• Record-Breaking Pregnancy: With a gestation period estimated at 3 years, they may have the longest pregnancy of any vertebrate.
• Breach potential: Unlike most sharks, basking sharks are known to leap completely out of the water, much like whales.
• Seasonal Travelers: They migrate thousands of miles each year, diving as deep as 3,000 ft (900 m) before returning to the surface.

Classification And Scientific Name

Aside from the name basking shark, which they’ve earned through their habit of floating gently along the ocean’s surface, these massive animals are also known as bone sharks or elephant sharks. Their scientific name is Cetorhinus maximus. Cetorhinus is taken from the Greek words meaning “sea monster” and “nose,” while maximus means biggest or greatest in size. The species is part of the Cetorhinidae family in the Chondrichthyes class.

Evolution And History

The oldest known member of the basking shark species is from an extinct genus called Keasius, which lived 66 million years ago. This ancestor gave way to Cetorhinus parvus, a now-extinct basking shark species indicated by the bristle-like gill rakers. Fossil records were discovered that can trace the basking shark back about 35 million to 29 million years to the Cenozoic era. The shark that we know today didn’t begin to appear until 23 million years ago, during the late Miocene era.

Appearance and Adaptations

This shark species is one of the most easily recognized by external appearance alone due to its notable size and distinct features. The average adult shark can extend up to 26 feet long from nose to tail, with some individuals reported reaching lengths of over 40 feet. Their great size is also accompanied by comparable mass, with an average mass of roughly 8,500 pounds. Their coloration ranges from a light brownish gray to nearly black, with the potential for mottled or pale skin as well.

Basking sharks have distinct gills that nearly encircle their entire body. Their gills are equipped with gill rakers, which are filament-like growths along the gills that catch plankton from the water passing through the slits. While their other physical features generally resemble other large shark species, like the great white, they sport a crescent-shaped tail fin that gives them another unique hallmark to distinguish them from their predatory cousins.

These sharks typically leave their massive mouth hanging wide open to maximize water intake as they slowly swim or float with the current. Their mouths are full of dozens of rows of tiny hooked teeth that can number well into the thousands. Their motion and feeding are relatively passive, although they can completely breach the surface of the water and engage in more rigorous swimming when threatened.

Behavior and Ecology

Basking sharks may gather in shoals of up to 100 individuals in rich feeding areas, but are generally solitary. They are highly migratory and may travel across entire oceans. Studies with satellite tags show they can dive to nearly 3,000 ft (900 m). However, they spend much of their time near the surface where plankton is abundant.

Distribution and Habitat

Geographically, the basking shark has a massive distribution that covers vast stretches of the Pacific and Atlantic oceans. They prefer cool to temperate climates, so their range does not include the Arctic, Antarctica, or tropical locations. However, they may pass through tropical waters during their long migratory trajectories that can extend for thousands of miles. They are encountered along the west coast of North and South America, as well as much of the European, Australian, and South African coastline.

Diet: What Do Basking Sharks Eat?

Basking sharks are adapted to feed on marine zooplankton, which are the myriad of microscopic organisms and larvae that live in ocean water. They are typically available in greater abundance near the surface, where there is sunlight, or near the bottom along the substrate. The sharks typically rely on currents and their slow swimming motion to force water into their mouth and through their gills so they can snag their food, occasionally closing their mouth to ingest quantities of trapped prey.

Predators and Threats

Their massive size makes them virtually immune to natural predators (except for orcas), but they are particularly vulnerable to humans. Their easy availability on the water’s surface, passive nature, and high historical population made them a tempting target for fisheries in the 19th and early 20th centuries. They were historically hunted for meat, liver oil, and fins. These sharks are also vulnerable to bycatch, boat strikes, and illegal shark finning. They are also susceptible to parasites like sea lampreys and cookie-cutter sharks.

Reproduction And Lifespan

Basking sharks usually move into shallower coastal waters when they are preparing to reproduce, which usually occurs between May and July. Individuals may have different partners throughout a single breeding season. Aerial and direct observation by researchers indicates complex courtship and mating procedures between adult sharks. A combination of synchronized swimming, biting, and nudging may serve as part of the ritual.

Basking sharks can live for over 30 years in the wild, and some experts believe their lifespan could reach up to 50 years. However, it takes an estimated 12 to 16 years for females to mature to the point where they can reproduce. While facts regarding reproduction in this species are limited to a few observations and specimens, researchers believe that they have a gestation period of around 3 years (the longest known pregnancy of any vertebrate) and give birth to litters of around 6 pups.

Conservation Status

Exact population numbers are unknown and can only be estimated by location, but the species is considered endangered by conservationists. There are an estimated 10,000 individuals in Atlantic Canada, which is one of their prime feeding grounds. Targeting by commercial fisheries as recently as the 1950s caused a noticeable decline in the worldwide population that has yet to recover. Their extremely slow maturation process and long gestation period, combined with the frequency of human encounters, are leading factors in population decline.

Today, basking sharks are protected in many countries, with strict bans on hunting and international trade. Conservation groups monitor populations via tagging and public sighting reports.

Human Interaction

Basking sharks are completely harmless to people, despite their intimidating size. They are popular in ecotourism, especially in the UK, Canada, and South Africa. Today, awareness campaigns are improving their reputation, which leads to them being better understood and protected.

Basking Shark vs. Whale Shark vs. Megamouth

Use In Fishing And Cooking

Historically, basking sharks served as an important source of raw meat and fishmeal, as well as leather from their skin and oil extracted from their liver. Some modern fisheries still target them for their fins, a key ingredient in shark fin soup, and for various internal parts that are prized in local traditional medicines, particularly in Asia. However, many countries have imposed a moratorium on fishing due to a substantial ongoing decline in the global population.

Famous Sightings and Research

• Breaching basking sharks off Cornwall, UK, have been documented on film.
• Satellite-tagging projects have revealed incredible transoceanic migrations.
• Sightings remain unpredictable, making each encounter with this giant shark memorable.