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MCRP Port Jackson Shark Research Project (October 2010)

 

Marine Care Ricketts Point has commenced collecting data about the Port Jackson Sharks ((Heterodontus portusjacksoni ) (PJs for short) that arrive in the Sanctuary in late winter each year and disappear after Christmas. 

PJs grow up to 1.5 metres in length and usually live in rocky environments on, or near, the sea bed. They have strong, crushing teeth and their diet usually consists of sea urchins, molluscs, crustaceans and fish. They forage for their food at night when their prey are most active, and often use caves and rocky outcrops as protection during the day. 

The PJ has two similar-sized dorsal fins. Each fin has a spine at the leading edge, which is reputed to be venomous. The spines of juveniles can be quite sharp, but those of the adults are usually blunt. The spines are sometimes found washed up on beaches and have been mistaken for all sorts of things from bird beaks to goat horns. These spines are believed to have given rise to the common name of the family, 'Horn Sharks'.

PJs are creatures of habit. They can migrate up to 800 km north in summer, only to return in winter for the breeding season. The breeding season is usually from late winter into spring. The female lays an egg case which is a tough, dark brown spiral about 7-8 cm wide and 15 cm long. It is common to see them washed up on beaches. When first laid, the egg case is soft and the female uses her mouth to wedge it into a rock crevice where it hardens. One young shark emerges from the case after 10-12 months.

This is the first stage in a project that aims to answer questions like –

 

  • Exactly when do they arrive and depart?
  • Are numbers greater at various times?
  • Does arrival/departure depend on water temperature or other factors?
  • Do the same sharks come to the Sanctuary (and the same locations in the Sanctuary) each year?
  • Do they breed here?
  • Where do they migrate to and from?

 

We are therefore asking divers and snorkelers to report their sightings, for publication on the MCRP website.  You can send to sightings to the email address below or (if you are a MCRP member) enter your data directly – this will require allocation of a user name and pass word.

 

In your reports, try to include information about –

 

  • Place, date, time, length of dive
  • Weather and sea conditions
  • Location(s) – eg Shark Alley or the Trench (if you know these locations)
  • Numbers/sizes/sexes of PJs (smaller ones are usually males) in each location. 
  • Distinguishing features (markings, damaged fins, condition of dorsal spines)
  • Any juveniles or eggs?
  • Were they active, resting etc?
  • Anything else of interest

 

Take and send photos if you can.

 

PJs are considered harmless but they do have two large dorsal spines.  They should not be handled or harassed in any way.

 

Please contact me on This e-mail address is being protected from spambots. You need JavaScript enabled to view it if you would like any further information or have any suggestions about how this project could proceed.

 

Peter Dedrick