Port Jackson Shark
Heterodontus portjacksoni
The Port Jackson shark is in the family Heterodontidae, also known as bullhead sharks, which are characterised by a blunt rounded head with raised ridges over the eyes and two dorsal fins with associated venomous spines on the leading edge. In addition, they have a characteristic arrangement of sharp teeth at the front of each jaw and plate-like teeth at the back which are used for crushing bivalve molluscs. The Port Jackson shark is the largest species in the family, measuring up to 1.65 metres in length. They have identifying harness-like markings across the eyes, centrally down the back then across the sides to the pectoral and ventral fins. Female Port Jackson sharks are oviparous and produce up to 15 spirally flanged egg cases, which the female twists into reef crevices with her mouth. Hatchlings emerge after 12 months of incubation. The young, otherwise known as neonates, have an 89% mortality rate of dying before hatching. Females require approximately 11-14 years to reach maturity, compared to 8-10 years for males at 80 centimetres in length.
Port Jackson sharks migrate up to 800 km north in summer, to return to the same geographical location in winter for the breeding season. During this time this species often congregate in large open caves along shallow coastal reefs. They predominantly inhabit rocky environments on, or near the seafloor, though are also found in sandy and seagrass habitats. Port Jackson sharks are nocturnal feeders, and feed by drawing in water and sediment, then blowing waste sand out through the gills while retaining the food. Their diet consists of sea urchins, molluscs, crustaceans and fish. Unlike pelagic sharks, the port Jackson shark has the ability to pump water across the gills enabling a slow moving, benthic existence. This species is endemic to Australia and occurs commonly in southern Australian waters, from the Houtman Abrolhos Islands, WA to Byron Bay, NSW and around Tasmania.
Occurrence at the Busselton Jetty
The Port Jackson shark is occasionally encountered resting on sand near the seagrass beds next to the jetty or on the seabed underneath the structure.
Image by: S. Teede
