Scylla Serrata - Ecology

Ecology

A study on tidal flats in Deception Bay in Queensland found juvenile crabs (20–99 millimetres or 0.8–3.9 inches carapace width) were resident in the mangrove zone, remaining there during low tide, while subadults (100–149 mm or 3.9–5.9 in) migrated into the intertidal zone to feed at high tide and retreated to subtidal waters at low tide. Adults (150 mm or 5.9 in and larger) were caught mainly below the low tide mark, with small numbers captured in the intertidal zone at high tide.

These crabs are highly cannibalistic in nature and when another crab undergoes moulting the hard shelled ones attack the moulting crabs and devour them. The females can give birth to 1 million offspring which can grow up to 3.5 kilograms (7.7 lb) in size and have a shell width of up to 24 centimetres (9.4 in) wide.