Reproduction
Egg case of a Port Jackson Shark (AMS I.1417).
A Port Jackson Shark with an egg case in its mouth. Photo © L. Clarke. View larger image.
A group of Port Jackson Sharks lying in a gutter at Broughton Island, New South Wales. Port Jackson Sharks are creatures of habit. They can migrate up to 800 km north in summer, only to return in winter for the breeding season, usually to the same area and often to the same gullies and caves.
The breeding season is usually late winter and into the spring. At this time, divers regularly observe sharks congregating in caves, under ledges and in gutters (see image below).
Port Jackson Sharks are oviparous, which means that the female lays eggs. The egg case is a tough, dark brown spiral about 7 cm to 8 cm wide and 15 cm long. It is common to see them washed up on beaches.
The egg case is soft when laid by the female. She uses her mouth to wedge the egg case into a rock crevice where it hardens, and from which one young shark emerges after ten to twelve months. The Crested Horn Shark has a similar-looking egg case with the addition of long twisted tendrils on the bottom end. These are often attached to seaweed. Female Port Jackson Sharks mature at 11 to 14 years of age, whereas males only take around 8 to 10 years.
Sharks can be oviparous (like the Port Jackson Shark), viviparous (give birth to live young), such as the Blue Shark or ovovivaparous (produce eggs which stay in the female and hatch inside the parent with no placental connection), such as the Grey Nurse Shark.
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Reproduction
Mature female Port Jackson sharks move to inshore reefs accompanied by some males beginning in July and August. They mate on coastal reefs and of the coast of New South Wales. Many males do not participate in breeding and remain in deeper water offshore. Breeding sharks congregate in caves but little is known about courtship and pair formation. (Rogers, 2000)
Port Jackson sharks are oviparous. During August and September, females lay 10 to 16 eggs in shallow reefs at depths of 5 to 30 meters. The egg cases are brown, spiraled structures that the females wedge into rock crevices. Females will hold an egg case in their mouth and insert it into a safe crevice. Females usually use the same breeding sites each year. Port Jackson sharks have been seen eating their own egg cases, but they have never been seen breeding. The young hatch out of the egg case after 10 to 12 months. (Budker, 1971; McGrouther, 2005; Rogers, 2000)
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