Port Jackson shark

Species of shark

The Port Jackson shark (Heterodontus portusjacksoni) is a nocturnal, oviparous (egg laying) type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large, blunt head with prominent forehead ridges and dark brown harness like markings on a lighter grey brown body, and can grow up to long. They are the largest in the genus Heterodontus. The Port Jackson shark is a migratory species, traveling south in the summer and returning north to breed in the winter. It feeds on hard shelled mollusks, crustaceans, sea urchins, and fish. Identification of this species is very easy due to the pattern of harness like markings that cross the eyes, run along the back to the first dorsal fin, then cross the side of the body, in addition to the spine in front of both dorsal fins.

The Port Jackson shark is endemic to the temperate waters around southern Australia and can be found in an area stretching from southern Queensland, south to Tasmania, and west to the central coast of Western Australia. Dubious reports exist of catchings as far north as Western Australia's York Sound. A single specimen of this species was collected in a set net at Mākara, Wellington in 1954. Two more specimens reported as being from New Zealand were presented to the British Museum however although these two specimens have been located they have no information on their collection location to confirm this assertion. It usually lives at depths of less than , but has been known to go as deep as
The shark's territory is habitually on or near the sea bottom, which is also its feeding area. Rocky environments are the most common habitat, though sandy and muddy ones, as well as seagrass beds, are sometimes used. or near other sheltering positions such as rocky outcrops.

The Port Jackson shark is a nocturnal species which peaks in activity during the late evening hours before midnight and decreases in activity before sunrise. The females arrive later and stay later perhaps as a means to reduce egg predation upon their newly laid eggs. Both sexes show philopatry and high site fidelity. These sensors function like Fitbits, but for sharks, and are commonly used in fish and shark species to identify important behaviours like resting, swimming and feeding.

Port Jackson sharks can grow up to long As many as eight pairs can be laid during this period. The eggs mature for 10–11 months before the hatchlings, known as neonates, can break out of the egg capsule. The eggs have been assessed in recent studies as having an 89.1% mortality rate, mostly from predation. Juvenile Port Jackson sharks, on the other hand, do not appear to be social. A captive study showed that these juveniles did not prefer to spend time next to other sharks, even when they were familiar with each other (i. e. tank mates). Juvenile Port Jackson sharks have unique personality traits, just like humans. Some were bolder than others when exploring a novel environment and they also reacted differently to a stressful situation (in choosing a freeze or flight response). Juvenile Port Jackson sharks are also capable of learning to associate bubbles, LED lights, or sounds with receiving a food reward, can distinguish different quantities (i. e. count), and can learn by watching what other sharks are doing. At least in some of these lab experiments males are shyer than females and boldness increases with consecutive trials of the same experiment. In experiments with different music genres, none of the sharks tested learned to discriminate between a jazz and a classical music stimulus.

Although listed as "Least Concern" on the World Conservation Union (IUCN) Red List, the shark's egg capsules experience very high mortality rates (estimated at 89.1%). Its status is otherwise largely unknown. Predators of the species are also unknown. Though crested bullhead shark (Heterodontus galeatus) are known to prey upon Port Jackson shark embryos, the biggest threat is probably from other sharks such as white sharks and the broadnose sevengill shark (Notorynchus cepedianus).