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Greenland shark - Somniosus microcephalus

With an average adult length between 8 and 15 ft to a maximum of 24 ft, the Greenland shark is the Arctic’s largest fish. It is native to the north Atlantic and the Arctic and is the only shark to tolerate such temperatures throughout the year; its preferred range seems to be 30-50°F. It can be observed from the surface to depths of almost 7,218 ft. The Greenland shark is believed to be an opportunistic feeder and a scavenger primarily; if prey is too large to swallow whole, it is able to pin it in place with pointed upper teeth and cut round “plugs” from it with wide, curved bottom teeth by swinging its head in a circular motion. 90% of the observed Arctic population are host to the parasitic copepod Ommatokoita elongata, which consumes its corneal tissue and causes partial blindness, but its habitat and depths renders its sight useless. The only confirmed predator of the Greenland shark is the sperm whale, although it is also known to be cannibalistic in the presence of individuals deceased or in distress. Currently classed as Near Threatened and taken as bycatch, it has been historically targeted for its rich liver oil but the extremely high concentration of urea and trimethylamine oxide in its flesh renders it toxic. There is very limited data at present on its lifespan except for a single scientific paper that showed a size increase of just over 2 inches in 16 years on one shark; this growth rate suggests that a fully grown Greenland shark could be over 200 years old, potentially making it the longest-living vertebrate on the planet.

Blue shark - Prionace glauca

Widespread throughout the world’s temperate and tropical waters, the blue shark is a pelagic species that is usually encountered in the open ocean but can be spotted inshore where the continental shelf is narrow. It can be found from the surface (in cooler waters) to a depth of approximately 1148 ft (in more tropical areas) and is highly migratory; its movements seem to be based on reproduction and prey distribution. The blue shark’s diet consists mostly of cephalopods, crustaceans and bony fishes, but it is also known to consume sea birds and cetaceans (possibly as carrion). Its colouration - deep blue on the dorsal side and bright white underneath - is camouflage in the open ocean and referred to as countershading. It is viviparous, with females delivering an average of 35 pups per litter (although the maximum recorded litter size was 135 pups) after a 9-12 month gestation. The skin of the female is three times thicker than that of the male, as the blue shark’s courtship involves extensive biting from the latter. Adults can reach about 12.5 ft in length at their maximum. Though the blue shark is not a species targeted by commercial fisheries, it is frequently caught as bycatch: It is estimated that 10-20 million blue sharks are killed annually. It is also sought after by sport fishermen, and is currently classed as Near Threatened by the IUCN.

Nurse shark - Ginglymostoma cirratum

Native to the coastal tropical and subtropical waters of the Atlantic and the eastern Pacific, the nurse shark is a nocturnal species that spends the day resting under ledges or in reef crevices. Though it can be observed resting in close groups of up to 40 individuals, sometimes piled on top of each other, at night the nurse shark is a solitary hunter that seeks out stingrays, fish, molluscs, and crustaceans along the sea floor. It is also known to graze on algae and corals. The mouth is small but the nurse shark’s pharynx is large and bellows-like, enabling it to suck in prey at a high speed. Adults can achieve a length of about 14ft, making it the largest in the Ginglymostomatidae (nurse shark) family. Despite its wide distribution and apparent abundance in certain areas, there is not enough data to determine its overall status at present, though it is believed to be vulnerable to human impact (including pollution and disturbance from tourism) and some fisheries.

Lemon shark - Negaprion brevirostris

Found along the tropical and subtropical parts of the Atlantic and Pacific coasts of both North and South America as well as Africa’s Ivory Coast, the lemon shark’s name is derived from its coloration, which can appear a pale yellow. It is perfectly camouflaged for swimming over the sandy sea floor while hunting for bony fish and crustaceans, although it is also known to feed on sea birds, rays, and smaller sharks. Fully grown adults reach approximately 8-10ft in length. It is viviparous, with females giving birth to a litter numbering between 4-17 pups every other year after a 10-12 month gestation; the pups stay in and around the shallow “nursery grounds” in which they were born for several years before venturing further. The lemon shark is targeted by commercial and recreational fishermen and is particularly sought after for its fins, which fetch a high price in the shark fin trade. It is currently listed as Near Threatened by the IUCN.

Spinner shark - Carcharhinus brevipinna

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A remarkable hunting technique of this active, fast-swimming shark gives it its common name: it will speed upward through a school of fish with its mouth open while spinning on its axis, emerging completely from the water.Although the maximum known size is known to be 10 feet, the average adult attains a length of just over 6 feet. Found in subtropical and warm temperate waters around the world except the eastern Pacific, the spinner shark forms schools, and the northwest Atlantic population migrates inshore during the summer months to feed and reproduce. Because of confusion with the blacktip shark, there is some uncertainty in the distribution data for this species. Throughout its range, particularly in the southeastern United States, the spinner shark is considered Near Threatened by the IUCN due to its popularity among recreational and commercial fisheries; it is prized for its fins, liver oil, flesh, and skin.

Swellshark - Cephaloscyllium ventriosum

Native to coastal waters in the Eastern Pacific from central California to Chile, the swellshark is a nocturnal species that rests among the rocky reef during the day and hunts fish, crustaceans and molluscs at night. Adults reach an average length of about 3ft and are oviparous, with the female depositing only two egg sacks at a time among a rocky, algal-covered habitat. When threatened, it bends its body and grabs its caudal fin in its mouth before swallowing a large amount of water to double its size, making it difficult for a potential predator to bite or remove it from a crevice. It is also able to do this same behaviour with air if brought to the surface, and will let out a dog-like bark when expelling the swallowed water or air.

Basking shark - Cetorhinus maximus

Named because it is usually seen swimming slowly at the surface while feeding, as if sunning itself, basking sharks are second only to the whale shark in size with an average adult length of 22-29ft. It is one of three species of filter feeding shark and the only one to use just the continual passage of water to trap its planktonic food against its gill rakers as it swims - it is believed to be able to filter 2,000 tons of water in an hour. It has a wide distribution throughout the world’s boreal and temperate waters, although it is not known to be abundant. Due to its slow growth rate and long gestation, the IUCN Red List currently classes the species as vulnerable worldwide and endangered in the north east Atlantic and north Pacific, where it was heavily fished: The basking shark’s liver can account for 25% of its total weight, and its fins are among the most valuable in the international trade.

Blacktip reef shark - Carcharhinus melanopterus

A frequent sight in tropical Indo-Pacific reef habitats, blacktip reef sharks tend to have a very limited home range, remaining in the same area for years at a time. They are swift and active hunters, preying primarily on bony fish, cephalopods and crustaceans, and play a major role in the structure of the inshore ecosystem, where they are an apex predator. Like most species in the Carcharhinidae family it is viviparous, with females giving birth to 2-5 pups. Fully grown blacktip reef sharks can reach approximately 5ft in length.

Zebra shark - Stegostoma fasciatum

A nocturnal carpet shark native to the Indo-Pacific, zebra sharks spend most of the day resting on the sand and hunt for molluscs, crustaceans and fish on the reef at night. The caudal (tail) fin of the zebra shark can be almost the length of the body, achieving a maximum total size of just over 8ft long. The name is derived from the striped pattern of the young sharks. Though the species is doing well in Australian waters, it is classed worldwide on the IUCN Red List as Vulnerable due to the destruction of its coral reef habitat and heavy fishing for its fins, liver oil and meat.