Have you ever found a spiral shaped casing that looks like seaweed on the beach?
Fishermen call them “mermaid purses.” These spirals are actually the egg cases of a Port Jackson Shark.
Some sharks are oviparous, they lay eggs. Some sharks are viviparous and they give birth to live young. There is no parental care in sharks.
Port Jackson Sharks lay 10 to 16 eggs from July to October, the young take 9 to 12 months to hatch and are sustained by a yolk sac. They break out of the wide end of the egg when fully developed. The eggs are flange shaped and usually found wedged into rocks and under ledges, the flange helps them to stay wedged underwater during rough seas. The eggs are approximately 15cm long.
Male sharks of the same species are usually smaller than the females. When mating the male bites and holds the females pectoral (side) fin. Females have tougher, thicker skin but still sustain injuries during breeding season. Males have two claspers (penis) so they can copulate from either side.
Port Jackson sharks grow to 1.65m and are harmless. They have crusher plates and eat molluscs, sea urchins and crustaceans.
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