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Port Jackson Sharks

September 20, 2012 3 min read

Last weekend the Sarah Shark crew ventured down to the beautiful Nelson Bay, to capture the egg laying Port Jackson Sharks getting it on .. Heterodontidae style.

Chillin outside Mrs. Murphys Crack at Nelson Bay

Kieren and I making faces with the Sea God of Nelson Bay

This footage is for the 5^th episode of Sarah Shark and is titled Port Jackson: The ancient Shark. I had my heart set on doing an episode on these guys because they were my first ever shark experience.

Back in 2006, I decided that I best test my love for the ocean by plunging the depths on SCUBA. It was the middle of winter in Melbourne, and on the last day of my open water course I woke at 5:30am to a freezing outside temp of 3 degrees. On my drive to the dive shop, it began to hail … brilliant.

We were heading out to Popes Eye dive site off Portsea. By the time we geared up (in my 2-sizes-too-big 7mm hire wetsuit) and got on the boat, my hands, toes and lips were purple … and by the time we got to rolling off the boat my face was stinging from the hail and it was a little difficult to breathe.

The sea looked somewhat like this ;)

To say the conditions were horrid is a vast understatement, so much to say that 5 divers got on the boat, and only myself and 1 other were senseless enough to get in the water. On the upside, this was about 8m. We got to the bottom, swam around for a bit, then completed our final skills test – all the while I'm thinking “I beep-ing hate this! How can I beep-ing love the ocean, but beep-ing hate diving!? … beep!” It was then, at that perfectly hopeless moment that a Port Jackson Shark swam straight through my legs, circled around once, and then swam off. “Holy beep! This is awesome!” and I can honestly say I have thought that ever since.

Photo: Rowland Cain

So, anyway … I love Port Jackson Sharks, but not just for that reason.

Think PJs are boring? Think again.

First and foremost; the egg cases produced by Port Jackson sharks are amongst the most brilliantly bizarre in all of nature. Described as auger-shaped, the mother is able to avoid predators by wedging the spiral egg in crevices. Sadly though, this is not always effective, and eggs suffer from an 85% mortality rate.

Secondly, their rear teeth change as they grow. A mature Port Jackson will have 2 distinctly different types of teeth. In the front they have peg-like grasping teeth and molar-like crushing teeth in the rear. The functionality of this ‘change’ in rear teeth as they grow is really interesting. Juveniles feed on soft-bodied borrowing critters – which is well suited to their grasping teeth. Adult Port Jacksons prefer the hard-shelled beasties and as such, these molar-like teeth morph them into a ruthless nutcracker. Thus, adult Port Jacksons can both grab and crush almost any creepy-crawly that comes its way. However, in doing so, they have generated some mean enemies in the bivalve aquaculture industry.

Adult PJ Shark Jaw. Notice the front grasping teeth and the big rear crushing teeth.

Thirdly, (and probably most awesomely) PJs are like a homing pigeon. Tagging studies off SE Aust showed that PJs were highly migratory (travelling upwards of 850km) but would always make their way back to their home turf to mate.

One study, looked at the relocation of PJs from one area to another, and in every single case, the shark made its way back to its original ghetto. Now that’s loyalty! Many more studies backed this finding and it is now accepted that PJs have a well-developed spatial memory – developing memory maps as they frolic up and down the coast of Australia. Heck yeah!

Lastly, they have spines. Before each dorsal fin, is a small triangular spine. Fin spines were common in many ancient sharks, and have independently evolved in only two lineages of modern sharks, the bullheads (PJs) (order Heterodontiformes) and the dogfishes (order Squaliformes). This has proven to be an effective defense agent in juvenile PJs, stopping them from being swallowed by bigger and badder ocean beings.

Hopefully, I have managed to excite you about the gorgeous PJ shark … and simultaneously about Sarah Shark Episode 5. We got some pretty unreal footage!