The Port Jackson Shark (Heterodontus Portusjacksoni)
- English Port Jackson shark
- French: Requin dormeur taureau
- Spanish: Dormilón toro
- Local Names: Bullhead shark, Bullhead, Pigfish, Oyster-crusher or Oyster crusher, Tabbigaw.
Diagnostic Features Of The Port Jackson Shark
Diagnostic features are supraorbital burrs at the lower end of the interorbital space and concave deep burrs, which are less than half the length of the eye. The lateral stem densities are large and rough. The anterior retaining tooth tip is a cusplet in adults, while the posterior molariform tooth is not carined, but extended and rounded. The penultimate dorsal fin has a length of 21-24, “while the anal and caudal space amounts to 10-13% of the total length. Field marks on the dorsal fin spine and anal fin are present, and the color pattern is striking, with a number of harness-like narrow dark stripes on the back, which are unique for this species.
114, precautionary number: 76-81, monospondylousprecaudal: 37-39, diplospondyspondyloustransition count: 37 to 43, pre-first dorsal fin spine count: 15-17, count of diplospondylousprecaudal transition on the second dorsal fin spine: 9-14. The first dorsal fin (spine) is directed from the young to the adult; it is the origin of the insertion of the front pectoral fin (pectoral fin from the middle base to the back of the fifth Gili-opening); after the introduction into the front pelvic fin, the pelvic fin at the first dorsal fin is free opposite the pelvic fin; the dorsal fin is high, rounded, angular and fallow, with a height of 12-16% of the total length; it has a somewhat larger pelvic fin than the second dorsal fin, and the second fin has its origin at the rear tip; the second pelvic fin is also round and angular, wrinkled and somewhat larger than the first. The anal fin is subeckig and rounded and folds likewise at the top; the anterior lower tail fin lies three times as long in the anal caudal as the anal fin base.
The egg shell is a flat, thin spiral flange with a diagonal housing axis and a pair of short, slender tendrils from the housing tip to the flange, four to five in a row.
Colour Of The Port Jackson Shark
Background colour of surface gray to light brown to whitish, distinctive black striped harness marks on the body and fins, light to dark spots on the head, narrow dark bars on the interorbital surface, one narrow dark black band around the eye fin, abrupt dark tip of the white dorsal fin at the tip of the hatches, whirlfins and body color patterns in adults. Larger types become approximately 70-165 cm big.
Distribution Of The Port Jackson Shark
Western and South Pacific, temperate to subtropical South Australia, New South Wales, Victoria, Tasmania, South Western Australia and the West Coast; suspect records from southern Queensland, the tropical northern coast of Western Australia and New Zealand; a single straggler from Waif, Australia.
Habitat Of The Port Jackson Shark
Frequently as littoral, nocturnal ground-shark on the temperate Australian continental shelf and the topmost slopes, that reach from densely at the coast up to tides up to 275 m.
Biology Of The The Port Jackson Shark
The observation and tagging of these nocturnal species under water has elucidated their life history to a degree that few other shark species have achieved. Port Jackson sharks are loners and occur in small and large groups. On the coast, they prefer caves, sandy soils, open ditches and shallow rocky reefs as resting places during the day, although in some of these places, individuals can be found resting in a certain area. Strong selection has been shown to favour sites that are genetically identical to sites with fewer sharks.
However, abundant fluctuations were observed on shallow reefs in New South Wales, correlated with seasonal influx of adults and breeding and correlated with seasonal temperature fluctuations. Although these sharks are very social and easy to study underwater, little is known about their sociobiology and behavioral patterns. In the future, these will be clarified by electronic marking, night observation with video equipment in low light and observation of colonies in captivity in semi-naturalistic habitats. The sharks are social and rest at preferred resting places, with about 16% of the sharks occupying these places.
Data from tags indicate that the seasonal reef population is in a continuous flow, with individuals migrating to their preferred reef during the breeding season. Sharks are seasonal breeding pairs in which the young are separated by the size of the hatch and the adults by the sex. The sharks were thought to have developed spatial memory, meaning finding preferred resting and breeding sites is a long migration route. Sharks can be transported from resting places in Sydney Harbour up to 3 kilometres away to different locations from where they return to their original resting places. Individuals are able to visit preferred resting places and can travel a considerable distance from these places during the breeding season.
Mature females, accompanied by males, migrate from the reef to the Sydney area of New South Wales at the end of July and August, where mating takes place. Most mature males remain in deep water. In August, September, July and October the females lay 10-16-10-12 eggs in crevices in shallow shelters on the reef at a depth of 1-5 m (20-30 m) and in captivity each day lay a pair of eggs for 8-17 days. A wide spiral flange made of egg shells serves as an anchor to keep the eggs wedged between rocks.
According to Michael (1993) it was observed that adults eat their own eggs (H. Francisci). The eggs are arranged in such a way that their pointed ends lie in crevices, and females have been seen carrying them, indicating that they lay their eggs by picking them up with the wide ends and inserting them into the corresponding crevice. The crevice in which they deposit the eggshells is usually made of open sand, but eggshells have also been found wedged in underwater oil pipelines and tin cans. Females prefer traditional nesting sites, some of which have been used for many years.
The boys hatch in the age of approximately 9 to 12 months and move into the rearing-area in the bay and estuary. Most kittens that retreat to deep water in summer stay in mixed groups for several years with a gender ratio of 1: 1 in the nursery. At the beginning of sexual maturity, adolescents move into deeper waters and are divided into male and female groups. Several years of adolescence are spent on the outer edge of the continental shelf, where the male and female groups join the adult population. At the end of the breeding season, adult males move into deep water, followed by adult females at the end of September and October.
The observed ratio between adult men and women does not contradict the ratio of 1: 1. A small number of adults can return to the coast in March or April next year to breed on the reef, but most do not stay on the coast and very few sharks are present at the beginning of the next breeding season. Some adults move into deeper waters, while others migrate inland.
Studies of blood protein from Port Jackson sharks in various regions suggest that they form two populations: a southwestern one in Western Australia (northeast Victoria) and a northeastern one in New South Wales and southern Queensland. Migratory adult sharks are thought to migrate south into coastal waters before returning to their breeding reefs in deep offshore waters. The area stretches from Tasmania to the Sydney area and New South Wales and has an annual migration cycle. Blood protein evidence suggests that sharks use preferred breeding sites in three locations in south Wales to represent different sub-populations, indicating a high site specificity, as demonstrated by the recapture of sharks from longer-lasting areas. On the east coast of Australia, the Port Jackson sharks show a pattern of migration southwards, with brooding females migrating at least every 5-6 months, moving up to 850 km from the breeding reef and returning the next year to the same breeding reef.
Approximate estimates of maturity from captive growth data are 8-10 years for males and 11-14 years for females. Data on growth rates in the wild, tagging, re-measurement of tagged individuals and calibration of fins, spine and vertebral rings are not available. Data from sharks in captivity suggest that juveniles grow 5-6 cm per year and adults 2-4 cm per year.
The Port Jackson shark feeds mainly on invertebrates and echinoderms. Prey include sea urchins, starfish, polychaetes, large snails, shrimp, crabs, barnacles and small fish. Rubbish such as mammalian shreds, potatoes and orange peels are also picked up by sharks. Food in the stomach is broken down into small pieces, suggesting that sharks grind their food with their powerful jaws and heavy molar teeth.
The food is taken from below at night and searched in the substrate. Odor stimuli are considered important, but electrosensors and the sense of line also play a role in this process. Food is eaten after the last contact with the oral region.
Predators Of The The Port Jackson Shark
Although no predators of this shark are known, it is thought that adults are protected by their sedentary habits, cryptic nocturnal behaviour, fins and spines, and disturbing colour patterns. Kittens are thought to be vulnerable to predatory fish from other sharks and large benthic teleosts. Potential predators include large macro-predatory sharks such as the blunt white shark and seven-footed white shark, as well as large otariid seals. Other sharks and sharks with significant parasites in the fauna are cestodes, tapeworms, trematodes, flatworms, nematodes, roundworms, isopods, larvae, copepods, fish lice and leeches.
Size Of The The Port Jackson Shark
The maximum total length is up to 165 cm, but is very rare with up to 137 cm. Males and adolescents are 50-80 cm long, 70-80 cm tall and reach at least 105 cm, females and adolescents 65-84 cm, adults 80-95 cm and reach at least 123 cm and adult females are 25 cm longer on average than adult males. The eggshell is 13-17 cm long and 5-7 cm wide at the wide end. The size of the hatch is 23-24 cm.
Human Impact On The Port Jackson Shark
They are caught for commercial fishing as bycatch from bottom trawls, beach chairs, anti-shark nets, GILI nets on the south coast of Australia or by recreational anglers with rods and reels. Not used as food, i.e. Interest in fisheries is low and the impact is therefore minimal.
Sharks are held for public aquariums in Europe, the United States and Australia and are an obvious candidate to showcase shark resistance and attractive colors and patterns. Divers can observe sharks, but they are not a special focus of ecotourism diving. Port Jackson Sharks are generally considered harmless to humans.
- 1908: Ogilby
- 1940: Whitley
- 1941: Fowler
- 1942: Smith
- 1970, 1971: McLaughlin and O’Gower
- 1972: Taylor
- 1973: Reif
- 1978: O’Gower and Nash
- 1993: Michael
- 1994: Last and Stevens
- 1995: O’Gower
- 1998: Compagno and Niem