Breeding
Sydney rock oysters are "broadcast spawners", that is, eggs and sperm are released into open water where fertilisation occurs. Within hours of fertilisation, the eggs develop into free-swimming planktonic larvae. The larvae swim in estuarine and coastal waters for up to three weeks, during which time they develop transparent shells and retractable feet. The larvae then settle on clean substrates using their feet to find suitable sites. The larval foot is resorbed once the larva is attached. The shell darkens and the small animal takes on the appearance of an adult oyster.
Growth rates vary with local conditions, but they generally reach 50 g in three years. Sydney rock oysters may change sex during life. Many start out as males and later change to females. About 60% of prime eating oysters are female. Selective breeding has reduced the time to market size from three to two years. Great success in selection for disease resistance to two protozoan diseases of oysters, namely, QX disease Marteilia sydneyi and winter mortality Bonamia roughleyi has been achieved.
Oysters are filter feeders, straining planktonic algae from the water. Birds, fish, stingrays, mud crabs and starfish all eat Sydney rock oysters, with the Australian pied oystercatcher being particularly fond of them.
Read more about this topic: Sydney Rock Oyster
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