SHARK, BROAD NOSE SEVEN GILL
The Broadnose Sevengill Shark is the only extant member of the genus Notorynchus, in the family Hexanchidae. Length at birth can be 40–45 cm , a mature male length is 1.3-1.7 m, mature female length is around 2 m. The longest found is 2.9 m. An opportunistic predator, the broadnose sevengill preys on a great variety of animals. It has been found to feed on sharks, rays, chimaeras, cetaceans, pinnipeds, bony fishes, and carrion. These sharks occasionally hunt in packs to take down larger prey, using tactics such as stealth to succeed. This sevengill, like all other members of Hexanchiformes, is ovoviviparous. After a 12 month gestation period, the female moves to a shallow bay or estuary in order to give birth to a large litter of up to 82 pups. The juveniles remain in this nursery for a couple of years before venturing out. The probable predators of this species are larger sharks. It is considered potentially dangerous to people, but the only confirmed attacks have been on divers.
The Broadnose Sevengill Shark 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.
Along the South African coast, fishermen most often catch Broadnose Sevengills in patches of dirty water, upwelled by strong southeasterly winds or caused by river runoff, tidal movements, or wave action. When winds or currents change and the discolored water is dispersed, the sharks often cease taking baits. This pattern suggests that Broadnose Sevengills may take advantage of poor visibility to conceal themselves, enabling them to ambush prey from close range and thus increase their chances of successful feeding. They will take almost any bait although live fish seem to be the best for this type of shark. Fish with medium to heavy tackle, size 1/0 to 6/0 hooks. The best time to fish this shark is at night.
The Broadnose Sevengill Shark has so far been found in the western Pacific Ocean off of China, Japan, Australia, & New Zealand, the eastern Pacific Ocean, and the southern Atlantic Ocean off of Argentina and South Africa. Large, old individuals tend to live in deep offshore environments as far down as 136 m. However, most individuals live in either the deep channels of bays, or in the shallower waters of continental shelves and estuaries. These sharks are mainly benthic in nature, cruising along the sea floor and making an occasional foray to the surface.
The Broadnose Sevengill Shark occurs in most temperate seas. In Australia it is known from the central coast of New South Wales, around the south of the country, including Tasmania, and west to south-western Western Australia.
The Broadnose Sevengill Shark is present in most parts of the coastal area of New Zealand.