Student Stuff

Port Jackson Shark
Heterodontus portusjacksoni (Meyer, 1793)

A Port Jackson Shark photographed at Shark Point, New South Wales. Port Jackson Sharks can easily be recognised by the distinct harness-like pattern on the side of the body. View larger image.

Common name

Port Jackson Shark

Scientific name

Heterodontus portusjacksoni
heteros - different (Greek)
dont - tooth (Greek)

Refers to the pointed front teeth and the blunt rear teeth.

portusjacksoni - named after Port Jackson (Sydney Harbour)

Family name

Heterodontidae
heteros - different (Greek)
dont - tooth (Greek)
idae - suffix meaning that this a family name. All animal family names end in -idae.

Size

Heterodontid sharks range in size from the 59 cm long Galapagos Bullhead Shark Heterodontus quoyi, found in the Galapagos Islands and the offshore islands of Peru, to the largest species in the family, the Port Jackson Shark, which can grow to 1.65 m. More commonly, however, the males grow to 75 cm and the females between 80 cm and 95 cm. When they hatch, juvenile Port Jackson Sharks, called pups, are about 25 cm long.

Number of species

There are over 370 species of sharks world wide, 166 of which occur in Australian waters. The family Heterodontidae has eight species all in the genus Heterodontus, three of which are found in Australian waters. These are the Port Jackson Shark, the Zebra Horn Shark, Heterodontus zebra, and the Crested Horn Shark.

Distribution

The family Heterodontidae is found in tropical and temperate marine waters in depths down to 275 m, although most are found in depths less than 100 m. The Port Jackson Shark occurs in southern Australian waters from southern Queensland south to Tasmania and west to the central coast of Western Australia.

There are some questionable records of the Port Jackson Sharks being caught as far north as York Sound in Western Australia. The species has been recorded only once from New Zealand. Studies of Port Jackson Shark genetics suggest there may be two populations in Australia, one occurring from southern Queensland to New South Wales and the second from north-eastern Victoria to Western Australia.

This image shows a Port Jackson Shark in a typical rocky habitat at Bowen Island, Jervis Bay, New South Wales. In the foreground are black sea urchins, Centrostephanus rodgersi, one of the sharks preferred foods.

Habitat requirements

Port Jackson Sharks usually live in rocky environments on, or near, the bottom. Sometimes they are found in muddy and sandy areas, or where seagrass occurs. Their diet usually consists of sea urchins, molluscs, crustaceans and fish.

They forage for their food at night when their prey are most active, and often use caves and rocky outcrops as protection during the day.

Structural, physiological and behavioural adaptations

Port Jackson Sharks are considered harmless to humans, although the teeth, whilst not large or sharp, can give a painful bite. Port Jackson Sharks are quite distinctive blunt headed-sharks that lay eggs. Only the heterodontid sharks have the combination of no anal fin and spines on the leading edge of the two dorsal fins.

Three Port Jackson Sharks lying on the bottom at Broughton Island, New South Wales.

Markings

Port Jackson Sharks have harness-like markings which cross the eyes, run along the back to the first dorsal fin, then cross the side of the body. This recognisable colour pattern makes it very easy to identify this species.

Spines

The Port Jackson Shark has two similar-sized dorsal fins. Each fin has a spine at the leading edge, which is reputed to be venomous. The spines of juveniles can be quite sharp, but those of the adults are usually blunt.

The spines are sometimes found washed up on beaches and have been mistaken for all sorts of things from bird beaks to goat horns. These spines are believed to have given rise to the common name of the family, 'Horn Sharks'.

The anterior (front) and posterior (back) dorsal fins of a Crested Horn Shark from the Australian Museum Fish Collection (AMS IB.1503).

Teeth

When most people think of shark teeth, they think of large, sharp teeth like those in the film 'Jaws'. Not all sharks have teeth like these. The serrated teeth of the Tiger Shark, right, are designed for cutting large prey into chunks for swallowing.

The teeth of the Port Jackson Shark are very different. They are not serrated, and the front teeth have a very different shape to those found at the back of the jaws, hence the derivation of the genus and family names. The anterior teeth are small and pointed whereas the posterior teeth are broad and flat.

Jaws of a Tiger Shark (AMS I.27078-001).

Jaw of a Port Jackson Shark, upper at top of image (AMS I.12874).

These teeth, are perfect for holding, breaking and then crushing and grinding the shells of molluscs and echinoderms.

Juvenile Port Jackson Sharks have more pointed teeth and feed on a higher proportion of soft-bodied prey than adults. They can feed by sucking in water and sand from the bottom, blowing the sand out of the gill slits, and retaining the food which is swallowed.

A specimen from the Australian Museum Fish Collection (AMS IB.3427). A - first enlarged gill slit. B - four posterior gill slits.

Respiration

Port Jackson Sharks have the ability to eat and breathe at the same time. This ability is unusual for sharks which mostly need to swim with the mouth open to force water over the gills. The Port Jackson Shark can pump water into the first enlarged gill slit and out through the other four gill slits.

By pumping water across the gills, the shark does not need to move to breathe. It can lie on the bottom for long periods of time, a behaviour that is observed at mating time (see below).

Reproduction

Egg case of a Port Jackson Shark (AMS I.1417).

A group of Port Jackson Sharks lying in a gutter at Broughton Island, New South Wales.

Port Jackson Sharks are creatures of habit. They can migrate up to 800 km north in summer, only to return in winter for the breeding season, usually to the same area and often to the same gullies and caves.

The breeding season is usually late winter and into the spring. At this time, divers regularly observe sharks congregating in caves, under ledges and in gutters (see image below).

Port Jackson Sharks are oviparous, which means that the female lays eggs. The egg case is a tough, dark brown spiral about 7 cm to 8 cm wide and 15 cm long. It is common to see them washed up on beaches.

The egg case is soft when laid by the female. She uses her mouth to wedge the egg case into a rock crevice where it hardens, and from which one young shark emerges after ten to twelve months. The Crested Horn Shark has a similar-looking egg case with the addition of long twisted tendrils on the bottom end. These are often attached to seaweed. Female Port Jackson Sharks mature at 11 to 14 years of age, whereas males only take around 8 to 10 years.

Sharks can be oviparous (like the Port Jackson Shark), viviparous (give birth to live young), such as the Blue Shark or ovovivaparous (produce eggs which stay in the female and hatch inside the parent with no placental connection), such as the Grey Nurse Shark.

Follow-up questions

Name another family of sharks that have dorsal fin spines.
One of the three species of Heterodontus found in Australia, also occurs in Japan. Which one?
The tail of the Port Jackson Shark looks quite different to that of the White Shark. Can you explain the differences based upon the lifestyle of the two species?