Port Jackson Shark.
Stout body. Large square head with prominent ridges above eyes. Two tall dorsal fins with pointed apexes; each with a spine at its origin. First dorsal fin origin anterior to pectoral fin insertion. Second dorsal fin origin level with pelvic fin insertion. Pectoral fins much larger than first dorsal. Pelvic fins smaller than second dorsal fin. Large, triangular caudal fin with prominent subterminal notch.
Dorsal coloration may be cream, light brown, or greyish with a reddish-brown or black bridle pattern. Juveniles usually much lighter than adults.
Maximum length usually does not exceed 165cm but there is one record of a whopping 237cm animal. Size at birth 18-31cm.
Port jackson sharks vary greatly in size by region, with east coast animals attaining much greater lengths than west coast animals.
Temperate seas. Sandy bays adjacent to rocky reefs and in kelp. From intertidal to at least 275m. Often found in shallow bays.
Temperate Australia. Found from Byron Bay southward, around the south coast (including Tazmania), to the Abrollos in the northwest. Records from Queensland may be misidentifications.
One verified record from New Zealand may be a vagrant that overshot Tasmania or possibly an aquarium release.
Although the Port Jackson Shark is a large bycatch component of several fisheries across its range, most individuals are returned to the water alive and post-release stress studies have shown that the species is very resilient to capture stress from gillnet, trawl, and longline gear, suggesting high post-release survival rates. The estimated decline of the Port Jackson Shark in Bass Strait between 1973-74 and 1998-2001 has now ceased and has been reversed as fishers no longer persecute the species. This decline was only observed in a small proportion of the species’ range and standardized catch-per-unit-effort from an observer program does not support the decline observed in the shark abundance surveys. In addition, a rapid semi-quantitative ecological risk assessment method showed that the Port Jackson Shark is at low risk from several fisheries because of its low catch susceptibility. The effects of fisheries on the Port Jackson Shark in other parts of its distribution are likely to be negligible and habitat modification and other environmental factors do not appear to be a threat to the health of the population. There is currently no evidence to suggest that the Port Jackson Shark faces any risk of extinction, justifying a listing of Least Concern.
Citations and References
Huveneers, C. & Simpfendorfer, C. 2015. Heterodontus portusjacksoni. The IUCN Red List of Threatened Species 2015: e.T39334A68625721. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T39334A68625721.en. Downloaded on 01 December 2020.
Oviparous. Like other heterodontids, the Port Jackson shark lays auger shaped egg cases.
PJS’s deposit their egg cases in very shallow water, often less than 5m deep. They have been documented holding their egg cases in their mouths and rotating their bodies to literally screw the eggs into cracks in the reef.
The Port Jackson shark’s diet is composed of sea urchins, other invertebrates, and small fishes.
Considering that heterodontid sharks are relatively poor swimmers, some tagged Port Jackson sharks migrate over impressive distances (up to 850 miles) from their breeding grounds in the northern part of their range, to their summer hunting grounds in South Australia and Tasmania. Others simply disappear for the summer; probably moving into deep water where there are no acoustic receivers to record their presence.
During the breeding season, Port Jackson Sharks exhibit a high level of site fidelity, with males/females spending about 90/85% of their time, on a single breeding reef and coming back to the same sites year after year (C. Brown and N. Bass, pers. comm., February 2015).
Reaction to divers
Very easy to approach. Remains motionless unless closely molested, at which point port jackson sharks usually retreat deeper into crevices or move to a quieter resting place.
Port Jackson Sharks are relatively abundant along the coast of New South Wales. Nelson Bay, Sydney, and Jervis Bay seem to get a disproportionately high amount of sightings but this may simply be because they are dived more heavily than other spots.
On the west coast, I stumbled upon a nursery area where hundreds of juvenile Port Jackson sharks were sitting out in the open in a shallow bay next to a sea lion colony. PJs are known to return to the same breeding sites every year, so the presence of juveniles in that spot will probably be quite likely in early May; when I dove there.