Latin name

Heterodontus portusjacksoni

Other name

Heterodontus portusjacksoni

Identification

The Port Jackson shark has a slender, cylindrical body. They have a large head with a blunt and short snout. There are low supraorbital protrusions that merge smoothly behind the head. The nostrils are framed by long flaps of skin at the entrance and exit. There are spiracles behind the eyes. The mouth is rounded. Front teeth are small and pointed. Lateral teeth are larger, elongated and shaped like molars. Teeth are sharper in juvenile sharks.

Features of fish fins

The pectoral fins of these sharks are large and rounded. The dorsal fins are small. The first dorsal fin is slightly larger than the second. Its base begins above the midpoint of the base of the pectoral fins. There is a vertical spine at the base of both dorsal fins. The base of the second dorsal fin is located between the bases of the pelvic and anal fins. The base of the anal fin is posterior to the base of the second dorsal fin. There is a ventral notch on the edge of the upper caudal fin blade.

Fish colouring

The basic colouration of the Port Jackson shark is grey-brown. Dark stripes run from the head, starting from the interorbital space, down the body to the first dorsal fin, along the pectoral fins and down the entire body.

Distribution

Endemic to Australian coastal waters. They are divided into two populations, inhabiting waters from north-eastern Victoria to Western Australia and from southern Queensland to New South Wales.

Habitat

Subtropical marine demersal oceanodromous species. These sharks are found on the continental shelf, usually no deeper than 100 metres, with a maximum depth of 275 metres. They inhabit rocky coastal reefs.

Size

The maximum recorded length of this species is 165 centimetres, but they are usually found around 137 centimetres.

Behavior

Port Jackson sharks migrate seasonally. They swim south in the summer and return north in the winter, in time for the breeding season. These sharks are segregated by sex and age. These sharks are nocturnal. During the day they climb into secluded caves with sandy bottoms. Up to 16 individuals can gather in the most attractive shelters.

Food and feeding habits

Unlike most sharks, which have to move with their mouths open to breathe, these sharks are able to breathe and eat at the same time. They pump water through the first enlarged gill slit and release it through the other 4 pairs of gill slits, pumping water through the gills to supply themselves with oxygen. This is why sharks of this species can remain motionless on the bottom for long periods of time.

The diet of these sharks consists mainly of benthic invertebrates, mainly echinoderms. They prey on sea urchins, starfish, polychaetes, large snails, shrimps, crabs, mussels and small bony fish. Their stomachs sometimes contain debris such as pieces of mammalian fur and orange peels. Juvenile sharks, whose teeth are sharper than those of adults, prefer softer prey. They grind their food with their lateral molars, cutting it into bite-sized pieces. They hunt primarily by smell, although electro-reception also helps them navigate. Juvenile sharks are able to suck up prey buried in the sand, with the sand spilling out through the gill slits.

Reproduction

Port Jackson sharks reproduce by laying eggs. Breeding is seasonal. Adult females, accompanied by adult males, swim to offshore reefs near Sydney in July and August. Mating is thought to occur at the same time. Females lay 10 to 16 eggs in crevices on the reefs, usually at depths of 1 to 5 metres, although deeper (20-30 m) is also possible. The egg capsules are 13-17 cm long and 5-7 cm wide at the broad end. A spiral ridge wraps around the outside of the capsule, acting as an anchor. Females prefer to lay their eggs in specific locations and will spawn in the same 'nests' for years. The young hatch from the eggs after 9-12 months. They spend the first few years in natural nurseries - estuaries and bays - where they congregate in mixed-sex groups with roughly equal numbers of males and females. Juveniles move into deeper water and form sex-segregated groups. After several years on the outer edge of the continental shelf, juvenile sharks join the adults.

Towards the end of the breeding season, adult males go deep, followed by females in late September and early October. Some sharks remain at depth in the open sea, while others migrate. A small number of sharks return to the shallow waters of the previous mating season the following year in March-April, but most return to the reefs by late summer. On the east coast of Australia, after the breeding season, females migrate south for 5-6 months, swimming up to 850km. Some sharks travel as far as Tasmania from Sydney.

Males reach sexual maturity at a length of 70 to 80 cm, corresponding to an age of 8-10 years, and females at a length of 80-95 cm at 11-14 years. The average length of males is 105 cm and 123 cm for females. Females are on average 25 cm longer than males. Newborns are about 24 cm long. Observations of sharks in captivity have shown that juveniles grow on average 5-6 cm per year and adults 2-4 cm.

Fishing

Port Jackson sharks are not fished commercially. They are regularly caught as by-catch in gill nets. These sharks are resilient and often survive release into the wild.

Relationship with a person

Traumatogenic. These sharks are not dangerous to humans, although they can bite annoying divers. Their meat is considered of poor quality and is not eaten. They are highly prized by aquarists. They have been successfully bred in large commercial aquariums.