Broadnose Sevengill Shark

Broadnose Sevengill Shark


Broadnose Sevengill Shark


Broadnose Sevengill Shark


Broadnose Sevengill Shark


Broadnose Sevengill Shark

Family: Hexanchidae

Identification: Bluntly rounded snout. Seven gill slits, posterior slits very short. Single dorsal fin set well back on body. Upper body sprinkled with small black spots and usually some white spots. Large size.

Size: At birth 34-45cm. Males mature at 130-170cm. Females mature at 200cm. Maximum recorded size 290cm. May possibly grow to 400cm.

Habitat: Coastal sandy bays and rocky shorelines up to the surf line. Larger individuals inhabit deeper channels. Recorded at 136m but usually found in 1-50m.

Abundance and distribution: Temperate coastal waters around the world. Southern Australia, New Zealand, Japan, Southern Africa, east and west coasts of south South America, and west coast of North America to Alaska.

Behavior and Diet: Cruises steadily along bays in search of food moving in and out with the tides. Prefers low visibility - night, turbid water, overcast conditions. Known to aggregate possibly for mating. Footage from the documentary Shark Quest shows a group of Broadnose Sevengill Sharks feeding together on a stingray carcass. Preys on sharks and rays, bony fishes and marine mammals.

Reproduction: Ovoviviparous (aplacental viviparous). Litter size 67-104. but may be higher. Gestation probably around one year followed by one year of recovery.

Observations: Broadnose Sevengill Sharks have been observed spy hopping - holding their heads above water and seeming to look around. This behavior is rare among sharks but has been regularly observed in Great White Sharks. it is possibly an adaptation to aid in the capture of marine mammals.

Similar species: The Bluntnose Sixgill Shark (Hexanchus griseus) has a very similar body shape but lacks the seventh gill slit and has less or no spots. The Sharpnose Sevengill Shark (Heptranchias perlo) has much larger eyes, a more pointed snout, and flattened, elongated pelvic fins.

Reaction to divers: The Broadnose Sevengill shark can become aggressive in baited situations e.g. towards spear-fishermen. In captivity it has bitten aquarium divers.

Bluntnose Sixgill Shark

Bluntnose Sixgill Shark


Bluntnose Sixgill Shark


Bluntnose Sixgill Shark


Bluntnose Sixgill Shark

Facts

Kingdom	Animalia
Phylum	Chordata
Class	Chondrichthyes
Order	Hexanchiformes
Family	Hexanchidae
Genus	Hexanchus (1)
Size	Length: 3.50 – 4.80 m (2)
Weight	480 – 720 kg (2)

Status

Classified as Lower Risk/near threatened (LR/nt) on the IUCN Red List (1).

Description

As its common name alludes, the bluntnose six-gill shark has a characteristically blunt rounded snout and six long gill slits on either side of its head, instead of the five that are usual amongst sharks (2). Other distinguishing features include its fluorescent green eyes, six saw-like teeth on each side of the lower jaw and the singular dorsal fin located close to the caudal fin (3). Colouring ranges from greyish-black to chocolate brown on the back, lightening to a greyish white underside, with a distinctive light stripe along the sides and white edging on the fins (4). Females tend to be slightly larger than males (2).

Range

The bluntnose six-gill shark is one of the wider ranging sharks, occupying temperate and tropical seas around the world (3).

Habitat

A reclusive deepwater species, found in the waters of continental and insular shelves and upper slopes (4). Juveniles may be found closer inshore while adults occupy deeper waters (1). This shark rests along the bottom during the day to depths of 2,000 meters, swimming close to the surface at night to feed (4).

Biology

Very little is known about this shark's social and mating behaviour, but they are thought to be solitary, coming together only to mate. Males are believed to nip a female's fins to entice her into mating (2). Reproduction in this shark is ovoviviparous; the young hatch from eggs retained within the mother so that she then gives birth to live young (2) (3). The exact gestation period is unknown, but it is thought to be longer than two years. Each litter can number from 22 to 108 pups and this incredibly large litter size suggests that juvenile mortality rates are high (2). Age determination is difficult in this species but males are believed to mature at 11 to 14 years, females at 18 to 35 years, and longevity to reach 80 years for both sexes (3).

The bluntnose six-gill shark is a skilled predator and may also scavenge, feeding nocturnally on a wide variety of marine organisms including other sharks, rays, bony fishes, squid, crabs, and seals (1) (2). Although reported as being sluggish in nature, they can reach remarkable speeds when chasing prey (2).

Frilled Shark

Frilled Shark


Frilled Shark


Frilled Shark


Frilled Shark

Geographic Range

Frilled sharks are wide ranging. They have been found almost worldwide, including the eastern Atlantic coast of northern Norway, the western Indian Ocean near South Africa, the western Pacific near New Zealand, and the eastern Pacific near the coast of Chile. (Compagno, 1984_

Habitat

Depth
100 to 1300 m
(328 to 4264 ft)

Chlamydoselachus anguineus, is found on continental shelves and the nearshore areas of large islands, although they are occasionally reported in open waters. They are mostly benthic and occur at depths from 100 to 1,300 meters. (Taylor et al., 2002)

Physical Description

Length
2 m (high)
(6.56 ft)

Frilled sharks, or eel sharks (Taylor et al., 2002), have a long slender body with an elongate tail fin, giving them an eel-like appearance (Compagno, 1984). The body tends to be a chocolate brown color. They have a small dorsal fin located well towards the tail, above the large anal fin, and in front of the highly asymmetric caudal fin. The pectoral fins are short and rounded (Taylor et al., 2002). Chlamydoselachus anguineus has six gill openings (most sharks have five). The first gill is continuous across the throat, while all the gills are surrounded by frilly margins of skin-hence the name "frilled shark." The snout is short and the lower jaw is long. The teeth are alike both on the upper and lower jaws, with three elongate, sharp cusps separated by two intermediate ones (Taylor et al., 2002; Nelson, 1994). Length is usually 2 meters (Miller and Lea,)

Lifespan/Longevity

Extreme lifespan (wild)
25 years (high)

Frilled sharks have never been kept in captivity. In the wild it is difficult to determine just how long these fish live. Because they are deep benthic creatures there is little information on lifespan. However, one source (Parker and Parker, 1999) estimates maximum lifespan at 25 years. (Parker and Parker, 1999)

Behavior

Chlamydoselachus anguineus is a slow-moving, deep water shark. They are among the slowest of shark species (Parker & Parker, 1999). Like most sharks, they are solitary. (Parker and Parker, 19