How do they reproduce?
The grey nurse shark uses oophagy and intra-uterine cannibalism to reproduce. This results in a maximum of two young per litter. Embryos hatch into the uterus at about 5.5 cm long. At lengths of around 10 cm they develop teeth and consume other embryos in the uterus. The single remaining embryo in each uterus (there are two) then feeds on unfertilised eggs as the female continues to produce them. The shark pups measure about 1 metre long at birth. Gestation is between 9–12 months and females only reproduce once every two years.

The timing of mating and pupping in Australian waters is unknown, but it appears that these sharks give birth at select pupping grounds. Many sharks with bite marks gained during mating, have been observed at Pimpernel Rock, New South Wales, during the months of March and April.

The age at maturity might be around 9–10 years. The average life span of a grey nurse is unknown although it is probably more than 16 years.

In New South Wales, a number of sites have been identified as grey nurse critical-habitats, which are vital to the survival of the species. Rules for divers and snorkellers in each grey nurse shark critical habitat area are:

• No scuba diving between sunset and sunrise;
• No blocking entrances to caves or gutters when the sharks are there;
• No feeding or touching the sharks;
• No chasing or harassing the sharks;
• No electronic shark repelling devices; and
• No underwater scooters.

In Queensland, there are restrictions on diving in three areas in the Moreton Bay Marine Park. In Western Australia, very little is known about the grey nurse shark population. They are rarely seen by divers but are caught as bycatch in other shark fisheries.

a) Locations of grey nurse habitats in New South Wales (© Environment Australia)	b) Locations of grey nurse sightings in Queensland                           (© Queensland DPI).

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