Author: (Meyer, 1793)
Field Marks:
Dorsal fins with spines, anal fin present, colour pattern with a conspicuous set of harness-like narrow dark stripes on the back, unique to the species.
Diagnostic Features:
Supraorbital ridges low, not abruptly ending behind eyes; molariform teeth in rear of mouth greatly expanded and rounded, without medial ridges. First dorsal origin over pectoral bases; apex of anal fin falling well short of lower caudal origin; anal base about 3 times in distance from anal insertion to lower caudal origin. Colour grey to light brown or whitish with a prominent black bar across head and down cheeks, a triangular black harness-like set of bars converging on the sides and back from the first dorsal origin, pectoral and pelvic bases, and a horizontal black stripe on the sides of the back and tail. Egg cases with simple, flat, broad paired spiral flanges, diagonal to case axis and with 4 or 5 turns visible on sides, case apex with very short tendrils.
Geographical Distribution:
Western South Pacific: Temperate and subtropical Australia (southern Queensland, New South Wales, Victoria, Tasmania, South and Western Australia), New Zealand (a single record, possibly as a straggler from Australia).
Habitat and Biology:
A common littoral, nocturnal bottom shark of the Australian continental shelves, ranging from close inshore in the intertidal to at least 172 m. Underwater observation and tagging of this species has elucidated its lifehistory to a degree attained with few other species. While inshore, the Port Jackson shark favours caves with sandy floors and open trenches of shallow rocky reefs as resting places, and almost all individuals in a given area will be found resting in relatively few of such sites. Strong selections is shown for favoured sites, and superficially identical sites nearby may have few or no sharks.
Pronounced fluctuations in abundance have been noted on shallow reefs off New South Wales, directly correlated with seasonal influxes of adults for breeding and inversely correlated by seasonal variations in temperature. Favoured resting sites may have up to 16 sharks occupying them. Data from tagging suggests that seasonal reef populations are in a state of continuous flux, with individuals moving in and out of their favoured reefs throughout the breeding season. Apparently individuals are capable of homing to favoured resting sites after ranging considerable distances away from them during the breeding season.
Breeding is seasonal, and development is oviparous. Mature females accompanied by some males move onto inshore reefs in late July and August in the Sydney area (New South Wales), and probably mating occurs at this time. Most mature males remain in deeper water offshore. During August and September (rarely in July and October) females lay 10 to 16 (commonly 10 to 12) eggs in rock crevices on shallow, sheltered reefs at depths of 1 to 5 m but occasionally down from 20 to 30 m. In captivity females lay a pair of eggs a day every 8 to 17 days. The egg cases are 13 to 17 cm long and 5 to 7 cm wide at the broad end, with broad spiral flanges that serve as anchors to keep the eggs wedge in the rocks. Females apparently favour traditional 'nest' sites which several apparently use collectively for many years. Apart from rock crevices, females may occasionally lay eggs on open sand, and eggs have been found wedged under an underwater oil pipeline and in tin cans. Eggs are oriented with their pointed ends into crevices, and females have been seen carrying eggs, suggesting that females lay their eggs, pick them up at the broad end, and insert them into appropriate crevices.
Young hatch after about 9 to 12 months and move into nursery areas in bays and estuaries. Some may retreat into deeper water during summer, but most juveniles remain in mixed groups with a 1:1 sex ratio on the nursery grounds for several years. At the beginning of sexual maturity adolescents move into deeper water and segregate into male and female groups. After several years of adolescence, apparently spent at the outer edges of the continental shelves, these groups join the adult populations.
Adult males apparently move into deeper water near the end of the breeding season, followed by the adult females in late September or October. Some adults move offshore into deeper water, but others migrate. Small numbers of adults may return to the inshore breeding reefs as early as March or April of the next year, but most do not stay inshore and few sharks are present until the onset of the next breeding season. Observed ratios of adult males and females are not significantly at variance with a 1:1 ratio.
On the east coast of Australia the Port Jackson shark shows a pattern of migration southward after breeding, with females migrating at least 5 to 6 months and moving up to 850 km south of breeding reefs before returning to the same sites the next year. Some may range as far south as Tasmania from the Sydney area in New South Wales in the annual migration cycle. It is thought that migrating adult sharks move southward ininshore coastal waters but return to their breeding reefs in deeper offshore waters.
Studies on blood proteins between Port Jackson sharks of different regions suggests that they form at least two populations, a western-southern one from western Australia to northeastern Victoria and a northeastern one from New South Wales and possibly southern Queensland. There is blood protein evidence to suggest that sharks using favoured breeding sites in 3 localities in New South Wales represent genetically distinct subpopulations, and indicates that the high site specificity shown by tagging and recapturing of sharks in this area is probably of relatively long duration.
Data from captives suggests that juveniles grow at about 5 to 6 cm per year and adults between 2 and 4 cm per year. Approximate estimates of age at maturity from captive growth data are 8 to 10 years for males and 11 to 14 years for females. So far, data is unavailable on growth rates in the wild from tagging and remeasuring of tagged individuals or from calibration and examination of fin spines or vertebral rings.
The Port Jackson shark feeds primarily on benthic invertebrates, with echinoderms the most important prey items. Prey items include sea urchins, starfishes, polychaetes, large gastropods, prawns, crabs, barnacles, and small fishes. Occasionally, garbage such as bits of mammalian fur, potato and orange peels are taken in by these sharks, although they are hardly gourmands for such items like tiger sharks (Galeocerdo). Juveniles with their smaller, more pointed teeth apparently take more soft-bodied prey than adults. Food items in stomachs are usually broken into small pieces, indicating that the sharks actively grind their food with their powerful jaws and heavy molariform teeth. Food is apparently taken at night on the bottom, and by searching close to the substrate. Olfactory cues are thought to be important, but electrosensing may play a role in this also. Food is eaten after final contact with the mouth region. Juveniles at least are capable of digging food out of the sand by sucking in water and sand and blowing it out of the gill covers. Respiration ean occur by pumping water into the first, enlarged gill slits and out the last four, which is thought to allow the shark to crush and grind its prey at leisure without having to take in water through its mouth and risk passage of food out the gill slits.
Predators of this shark are poorly known, but it is suspected that adults are highly protected by their sedentary habits, cryptic, nocturnal behaviour, and disruptive colour patterns. Juveniles in nursery grounds are thought to be more vulnerable to predation by other sharks and larger benthic teleosts. Adults are sometimes attacked by small predatory isopods, and eggs attacked by male Port Jackson sharks and possibly a gastropod drilling predator. As with other sharks, this has a sizeable parasite fauna, including cestodes, trematods, nematodes, isopod larvae, copepods, fish lice, and leeches.
This shark is considered harmless to people, though presumably it can deliver a painful nip when provoked as in H. francisci.
Size:
Maximum total length reported 165 cm, but apparently rare above 137 cm. Males are adolescent between 50 and 80 cm and mature between 70 and 80 cm to reach at least 105 cm; females are adolescent between 65 and about 84 cm and mature between 80 and 95 cm to reach at least 123 cm; adult females average about 25 cm longer than adult males. Size at hatching 23 to 24 cm.
Interest to Fisheries:
Apparently minimal; taken by bottom trawls, shrimp nets, beach seines, bottom longlines and by rod and reel, but probably little utilized.
Remarks:
Reif (1973) noted that the holotype of Heterodontus bonae-spei, supposedly from South Africa, is most probably a specimen of H. portusiacksoni with an erroneous locality label.
Type material:
Holotype: None. Type Locality: Botany Bay, New South Wales, Australia.