The only species in the family Cetorhinidae, Basking Sharks are also known as the Bone Shark, Elephant Shark, Sail Fish, and Sun Fish. They are migratory and overwinter in deeper waters. These slow-moving sharks feed on plankton and have long been fished by humans. While we’ve learned a few details about the lives of Basking Sharks, much of their world remains unknown to us.
What Makes The Basking Shark Unique?
The Basking Shark, or Cetorhinus maximus, is a very different species of shark. They are found in all of the world’s temperate oceans and are known as a cosmopolitan migratory species. Cosmopolitan migratory sharks swim near the surface to bask in the warmer waters and feed. Perhaps their most defining characteristics are their long gill slits that nearly encircle their entire heads and pointed snouts. They have a distinctive lunate caudal fin, lateral keels, and their dorsal fin tends to curl to one side when above the water’s surface.
The color of Basking Sharks can be highly variable dependent on the shark’s environment and condition. Typically, Basking Sharks are dark brown, black, or blue with white underbellies. Although the lifespan of the Basking Shark is unknown, scientists estimate Basking Sharks can live up to 50 years. At maturity they are about 15 to 20 feet (4.6 to 6 m) long, but have been known to grow up to 35 feet (10 m). They are the second largest fish in the ocean behind the Whale Shark and can weigh up to 4 tons (3.62 metric tons). Basking Sharks do not hibernate, but during winter they migrate to deeper waters to hunt zooplankton.
Basking Sharks Are Filter-Feeders
Thanks to their gill rakers, Basking Sharks can slowly filter-feed. They are known as passive feeders, eating the zooplankton, small fish, and other invertebrates that filter through their gill rakers. Unlike other filter-feeders that can suck or pump water through their gills, the Basking Shark can only move water through their gill rakers by swimming. Scientists do not believe that Basking Sharks can seek their food selectively, although they do have olfactory bulbs believed to be used to guide them toward food.
The mouth of a Basking Shark can be up to 3 feet (1 m) wide, which allows them to sift through up to 1,800 tons of water per hour. As feed, they move at about 2.3 miles (3.7 kilometers) per hour. Basking Sharks continually shed old gill rakers to make space for new ones.
Basking Sharks Have Few Predators
Perhaps given their large size, Basking Sharks have few known predators. Lampreys and Cookie Cutter Sharks are believed to attack Basking Sharks, although they are little match for these large creatures. White Sharks and Killer Whales may feed on them as they have been observed feeding on Basking Shark remains.
Basking Sharks Travel The Globe
Although they enjoy cool to temperate waters close to short and near the water’s surface, Basking Sharks move to depths of 3,000 feet (900 meters) in winter to feed on plankton living in the deep water. They migrate thousands of kilometers during the winter in search of deep-water plankton. Basking Sharks are social animals. They tend to spend their lives split into sex-segregated schools, typically numbering in from 3 to 4 sharks. However, Basking Sharks have been known to travel in schools of up to 100 individuals.
Basking Sharks are found all over the world’s oceans. Although they are slow-moving sharks, they can breach like Great White Sharks. Some scientists believe this is to remove parasite fish clinging to their skin, while others believe it could be a display of power and physique.
Basking Sharks Have Unique Mating Rituals
Basking Sharks likely don’t reach maturity until between the ages of 6 to 13. At maturity females measure up to 33 feet (10 meters) long, while males reach 30 feet (9 meters) in length. Gestation is believed to take between 1 to 3 years. The number of young a mother can carry is unknown, although one previously captured pregnant female was carrying 6 unborn fetuses. Basking Sharks are born ovoviviparously. This means the young hatch from eggs inside the mother and then are born live once fully developed.
Young Basking Sharks are born 47 to 79 inches (1.5 to 2 meters) in length. Since there is no placenta to nourish them, it is believed young feed on unfertilized eggs in the womb. They are not nurtured after birth and once born swim away. Mating occurs in early summer and involve displays of prowess and physique. Once impregnated, females move to shallow waters to give birth in late summer.
Basking Sharks Inspire Myths
Basking Sharks provided the foundation for scores of sea monster tales. They’ve also provided much to study in the realm of cryptozoology. Many of the Globsters, Sea Serpents, and Plesiosaurs found decomposing on beaches have turned out to be Basking Sharks. They are also mistaken for massive Great White Sharks, so they feed the myth that Megalodon may still be roaming our seas.
Basking Sharks Are In Danger From Humans
Basking Sharks are harmless to humans. However, they have been an important catch for centuries due to their various commercial uses. Basking Sharks are a source of food, their skin provides hide for leather, they are used in animal feed, and are prized for their large liver for producing shark liver oil. They are also hunted for their fins and cartilage.
Basking Shark fins are among the most valued and most expensive seafood products in the fishing industry. Although banned in many places, shark finning, which refers to cutting the shark fins and discarding the body back into the ocean, persists today. Without their fins, sharks cannot swim properly, and they will suffocate as they sink to the bottom of the seafloor. Although the Basking Shark has been protected from fishing in some territorial waters, they sometimes fall victim to fishing practices and illegal shark finning.
The International Union for the Conservation of Nature (IUCN) Red List of Endangered Species designated the Basking Shark as a vulnerable species, meaning they face a high risk of endangerment in the wild. Due to finning and accidental bycatch fishing by humans, their slow reproductive rate and long maturation time, they are facing possible extinction. So many groups are fighting for more protections for the species.
Basking Sharks are truly a different species of shark. As large, docile filter-feeders, that resemble Great Whites, they highlight the diversity of sharks even within subclasses. Though they have inspired countless myths, Basking Sharks are under constant threat from humans. So it is imperative to learn about these beautiful creatures, so we can work to protect them.