Port jackson 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 1.65 metres (5.5 ft) 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.
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NocturnalNocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal",...
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MolluscivoreA molluscivore is a carnivorous animal that specializes in feeding on molluscs such as gastropods, bivalves, brachiopods, and cephalopods. Known mo...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
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starts withPort Jackson sharks can grow up to 1.65 metres (5.5 ft) long and are similar to others of their genus, bearing a broad, blunt, flat head, an anal fin, and crests above its eyes. However, the species possesses characteristics that make them easily identifiable, such as their teeth and the harness-like markings which run for a majority of their body length. These markings run from their eyes to their first dorsal fin and then across the rest of their bodies. Both dorsal fins are close to equal size, each with a spine at the foremost edge. These spines are rumored to be poisonous. Other features that help distinguish them are their small mouths as well as their nostrils, which are connected to their mouths.
The sharks have grey-brown bodies covered by black banding, which covers a large portion of their sides and backs. One of these bands winds over the face and progresses to the shark's eyes. Another harness-shaped band goes around the back, continuing to the pectoral fins and sides. Thin, dark stripes are also present on the backs of Port Jackson sharks. These progress from the caudal fin to the first dorsal fin.
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. and on one occasion, it has occurred off the coast of New Zealand. Genetic studies suggest two Australian groups, one found from Northeastern Victoria to Western Australia and the second found from Southern Queensland to New South Wales. The species is believed to have originated somewhere off the coast of South Africa. It usually lives at depths of less than 100 metres (330 ft), but has been known to go as deep as 275 metres (902 ft).
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. During the day, when it is usually not active, it can be found in flat areas which offer some shelter from currents (including caves) 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. A study showed that captive and wild individuals displayed similar movement patterns and the sharks' movements were affected by time of day, sex, and sex-specific migrational behaviour.
This species completes an annual migration to breed in coastal embayments with males arriving first in harbours and bays along Australia's coastline. 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.
Port Jackson Shark movements have been quantified using tri-axial accelerometers. 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.
Male Port Jackson sharks become sexually mature between ages 8 and 10, and females at 11 to 14. They are oviparous, meaning that they lay eggs rather than give live birth to their young. The species has an annual breeding cycle which begins in late August and continues until the middle of November. During this time, the female lays pairs of eggs every 8–17 days. 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.
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).
In June 2018 the New Zealand Department of Conservation classified the Port Jackson shark as "Vagrant" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.
The shark has no major importance to humans. It is not an endangered species and is not used as a common food supply. It is, however, useful when scientists are hoping to study bottom-dwelling sharks and can be vulnerable to being caught as bycatch. It also does not pose any danger to humans. In October 2011 a man was bitten by a Port Jackson shark at Elwood Beach near Melbourne. The bite did not pierce the skin and the man was able to swim away while the shark was latched on to his calf.
