Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha and are the sister group to the Batoidea. Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period, though some fossilized chondrichthyan-like scales are as old as the Late Ordovician. The earliest confirmed modern sharks (selachimorphs) are known from the Early Jurassic around 200 million years ago, with the oldest known member being Agaleus, though records of true sharks may extend back as far as the Permian.
The great white shark, also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is the only known surviving species of its genus Carcharodon. The great white shark is notable for its size, with the largest preserved female specimen measuring 5.83 m (19.1 ft) in length and around 2,000 kg (4,400 lb) in weight at maturity. However, most are smaller; males measure 3.4 to 4.0 m, and females measure 4.6 to 4.9 m on average. According to a 2014 study, the lifespan of great white sharks is estimated to be as long as 70 years or more, well above previous estimates, making it one of the longest lived cartilaginous fishes currently known. According to the same study, male great white sharks take 26 years to reach sexual maturity, while the females take 33 years to be ready to produce offspring. Great white sharks can swim at speeds of 25 km/h (16 mph) for short bursts and to depths of 1,200 m (3,900 ft).
The blue shark, also known as the great blue shark, is a species of requiem shark, in the family Carcharhinidae, which inhabits deep waters in the world's temperate and tropical oceans. Averaging around 3.1 m (10 ft) and preferring cooler waters, the blue shark migrates long distances, such as from New England to South America. It is listed as Near Threatened by the IUCN.
The whale shark is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of 18.8 m (61.7 ft). The whale shark holds many records for size in the animal kingdom, most notably being by far the most massive living non-cetacean animal. It is the sole member of the genus Rhincodon and the only extant member of the family Rhincodontidae, which belongs to the subclass Elasmobranchii in the class Chondrichthyes. Before 1984 it was classified as Rhiniodon into Rhinodontidae.
The basking shark is the second-largest living shark and fish, after the whale shark. It is one of three plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sharks reach 7.9 m (26 ft) in length. It is usually greyish-brown, with mottled skin, with the inside of the mouth being white in colour. The caudal fin has a strong lateral keel and a crescent shape. Other common names include bone shark, elephant shark, sailfish, and sunfish. In Orkney, it is called hoe-mother, meaning "the mother of the picked dogfish".
The broadnose sevengill shark is the only extant member of the genus Notorynchus, in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large, thick body, with a broad head and blunt snout. The top jaw has jagged, cusped teeth and the bottom jaw has comb-shaped teeth. Its single dorsal fin is set far back along the spine towards the caudal fin, and is behind the pelvic fins. In this shark the upper caudal fin is much longer than the lower, and is slightly notched near the tip. Like many sharks, this sevengill is counter-shaded. Its dorsal surface is silver-gray to brown in order to blend with the dark water and substrate when viewed from above. In counter to this, its ventral surface is very pale, blending with the sunlit water when viewed from below. The body and fins are covered in a scattering of small black & white spots. In juveniles, their fins often have white margins.
The smooth hammerhead is a species of hammerhead shark, and part of the family Sphyrnidae. This species is named "smooth hammerhead" because of the distinctive shape of the head, which is flattened and laterally extended into a hammer shape, without an indentation in the middle of the front margin. Unlike other hammerheads, this species prefers temperate waters and occurs worldwide at medium latitudes. In the summer, these sharks migrate towards the poles following cool water masses, sometimes forming schools numbering in the hundreds to thousands.
The sharpnose sevengill shark, also known as one-finned shark, perlon shark, sevengill cow shark, sharpsnouted sevengill or slender sevengill, is a species of shark in the family Hexanchidae, and the only living species in the genus Heptranchias. Found almost circumglobally in deep water, it is one of the few species of sharks with seven pairs of gill slits as opposed to the usual five. The other shark species with seven gill slits is the broadnose sevengill shark. Though small, this shark is an active, voracious predator of invertebrates and fish. When caught, this species is notably defensive and will attempt to bite. It is of minor commercial importance.
The dumb gulper shark is a rare and endangered deepwater dogfish, found along the east coast of Australia and in isolated spots north and west of New Zealand. It is also known as the dumb shark, Harrison's deep-sea dogfish, or Harrison's dogfish.
The birdbeak dogfish is a dogfish shark of the family Centrophoridae found in the Pacific Ocean around Honshū, Japan, southern Australia, New Zealand, and Chile, and in the Atlantic Ocean from Iceland south to the Cape of Good Hope.
The rough longnose dogfish is a little-known deepwater dogfish. This species was described by Samuel Garman in 1906 and originally named Acanthidium hystricosa.
The bareskin dogfish is a little-known, deepwater dogfish shark of the family Etmopteridae. This species is found in the western Pacific from southern Japan to western and southeastern Australia as well as in New Zealand waters.
The New Zealand catshark is a catshark of the family Scyliorhinidae in the order Carcharhiniformes. This species is endemic to in the deep waters around New Zealand. Its length is up to 45 centimetres (18 in). The New Zealand catshark is a small, little-known deep water bottom shark. It is dark brown around the top with a few widely spaced pale spots, and white below. It feeds on bottom-living crustaceans. It is also completely harmless to humans.
The longnose velvet dogfish is a sleeper shark of the family Somniosidae, found circumglobally in southern hemisphere subtropical seas, at depths of between 230 and 1,500 m. It reaches a length of 130 cm. It has a diet consisting of predominantly mesopelagic fishes and squids.
The roughskin dogfish is a sleeper shark of the family Somniosidae, found around the world on continental shelves in tropical, subtropical and temperate seas, at depths of between 100 and 1,500 m. It reaches a length of 121 cm.
The whitetail dogfish is a very rare sleeper shark of the family Somniosidae, found from the eastern Indian Ocean round southern Australia to New Zealand, at depths of between 150 and 500 m. Its length is up to 1.1 m.
The white-bodied catshark is a catshark of the family Scyliorhinidae.
The southern Mandarin dogfish is a species of Mandarin dogfish shark in the genus Cirrhigaleus. It was distinguished from Cirrhigaleus barbifer, which lives in the North Pacific, on an expedition in the coral reefs near Australia in 2007. It is now known to live in the temperate waters in south-eastern Australia and from the Bay of Plenty region in New Zealand, at depths of 146–640 metres.
David William Sims is a British marine biologist known for using satellite tracking to study wild behaviour of sharks and for the Global Shark Movement Project. He is Senior Research Fellow at the Laboratory of the Marine Biological Association (MBA) in Plymouth, and a Professor of Marine Ecology in the National Oceanography Centre, Southampton at the University of Southampton, U.K.
Reef Life Survey is a marine life monitoring programme based in Hobart, Tasmania. It is international in scope, but predominantly Australian, as a large proportion of the volunteers are Australian. Most of the surveys are done by volunteer recreational divers, collecting biodiversity data for marine conservation. The database is available to marine ecology researchers, and is used by several marine protected area managements in Australia, New Zealand, American Samoa and the eastern Pacific.
Clinton holding a small Spotted Smoothhound Australian Museum
