Port Jackson Shark

(Heterodontus portusjacksoni)

I know the idea of �sharks� is scary to some people (me included) but once you see a Port Jackson shark you will realise there is nothing to be scared about these endearing looking sharks. They look shy and cute, not your typical heart stopping scary shark. Its no wonder divers look forward to their return every winter. They always remind me a big friendly puppy dog. Port Jacksons, commonly called PJs by most divers are starting to show up on local dive sites already, several have been seen on the right site of Bare Island and out at Cape Solander at Kurnell. If you have never had the chance to see these sharks before now is the time to hit the water and see your first PJ. Why not come along on one of our weekend or midweek dives and see the PJs.

There are also some great photos in Under Southern Seas edited by Neil Andrew or Australia by Roberto Rinaldi.

Scientific name
The PJs scientific name actually means �different teeth� and this is exactly what the PJ has, The PJs front teeth are small and pointed, where as the back teeth are broad and flat. Their teeth are perfectly adapted to their diet, which is discussed below.

Warnings
PJs are not dangerous but like all marine life, they are wild animals and should be treated with respect. PJs have a venomous barb in front of each dorsal fin. Some books I read indicated that this barb is very sharp in young PJs but it grows blunt as the shark matures. Apparently this barb even falls off sometimes and can be found washed up on the beach.

The PJ also has powerful jaws like most sharks, but their mouth is usually too small to be able to do any damage to a human. Common problems to watch out for when diving with PJs is to make sure a startled PJ doesn�t run into you! I once had a fleeing PJ swim into my head; let me tell you, they have hard heads.

Remember that the PJs are probably scared of the big brightly coloured bubble-blowing creature so try not to harass the PJs too much on your next dive.

Size and appearance
Pjs can grow to a length of 1.65m. But more commonly the males are about 75cm and the females are usually 80-95cm. The PJ has a blunt snout, and is usually a browny colour with a black triangular harness like set of bars converging on the sides and back from the start of the first dorsal fin and bases of the pectoral and pelvic fins. They also have a black strip which runs through to the eyes. It makes it look like the PJ is wearing some type of super hero mask.

The PJ has 5-gill slits and it is able to do a pretty nifty thing with its gills. A PJ can pump water into its first enlarged gill slit and out through the other four-gill slits. This enables it to lie on the bottom for long periods of time without moving. Most other sharks have to swim with their mouths open to forces water over the gills. The PJ has no need to do this. It is the perfect couch potato of the shark world.

Distribution & Habitat
PJs are distributed from Moreton Bay in Qld down to Tasmania and around to Houtman Abrolhos in WA. Apparently genetic analyses of the PJs in Australia suggest that there are two separate stocks of PJs within Australia. That there is one group which occurring from Queensland to Tasmania and another genetically different group extending from Victoria to Western Australia. There are also distinct sub groups within these groups, with Sydney having its own sub group of PJs which come back to the same spots every year to mate and lay eggs.

Food
Pjs feed at night, and if you ever do a night dive you have the chance to see these usually docile lazy looking sharks get very active. They feed on a wide variety of reef and sand dwelling invertebrates such as sea urchins, marine snails, crabs, molluscs and occasionally small fish as well.

Reproduction
PJs usually breed in late winter early spring. This is when we see large number of PJs laying around the bottom under leges and in caves. They usually return to the same area every winter to breed, this is often the same gullies or the same caves. Pjs usually migrates up to 800km north in the summer, and will migrate back north for the winter.

I could not find any good information on how the Pjs breed but I do know that after they breed the female usually lays 10-16 eggs around October. Most people have seen PJ eggs before as they tend get washed up on the beach. They are a tough, dark coloured, spiral looking eggs about 7-8cm wide and about 15cm long. They are usually soft when laid and become harder afterwards; they take about 10-12 months to hatch. After hatching the young Pj is on their own. Males become sexually mature around 8-10 years of age and females around 11-14 years of age.

References

• Under Southern Seas � The Ecology of Australia�s Rocky Reefs. Edited by Neil Andrews
• Australian Marine Life � the Plants and Animals of temperate Waters, by Graham J. Edgar
• Australia, by Roberto Rinaldi