There are several different types (species) of mud crabs. The most common are the green and brown mud crabs.

Mud crabs live in mangrove swamps and tidal flats. Juveniles eat zooplankton and other small molluscs and crustaceans. Adult mud crabs feed at night on mussels, scallops, small crabs and polychaete worms.

They burrow backwards into the mud using their large front claws for protection. Many animals like to eat mud crabs including sharks, crocodiles, turtles, rays, octopus, heron and large fish like cod and barramundi.

Like all crabs (decopods) mud crabs have ten legs. The front claws of a mud crab are large compared to the rest of the body. The last pair of legs are specialised, flattened to help the crab swim. If the large front claws are lost, they can grow again.

In 1992 a mud crab was found in the Swan River, which is a long way from where they like to live. The WA Museum has only one other recording of a mud crab being found in the Swan River. It is possible the mud crab was carried south by the Leeuwin Current.

When the mud crab breeds, the eggs are carried by the mother. The small specialised legs called swimmerets hold the eggs close to her body. When females are carrying eggs they are said to be in ‘berry’.

Scientific and other names
Mud Crab (Scylla serrata)

What they look like
Mud crabs have large claws and special flattened swimming paddles on their last pair of legs. These paddles will help them to swim when they are in the open sea. The hard shell that covers their body is called a ‘carapace’. The mud crabs carapace has nine teeth shaped points on both sides of their body. This is one way of telling the difference between mud crabs and other crabs.

Green Mud Crab - this species generally grows larger than the brown and is usually deep green in colour, with paler green mottling on the claws, legs and rear flippers.

The crab also has a pair of double spines situated just behind each claw and another pair on each wrist.

Brown Mud Crab - Generally smaller in size with both claws showing characteristic brown colouration, particularly on the underside. This species has only one single spine behind each claw and only one spine on each wrist.

Where they live
Mudcrabs in Western Australia can be found in most marine environments from the Northern Territory border in the north, around the coast to Shark Bay in the south.

They like to burrow into mud banks in estuaries and mangroves. Mudcrabs can be caught in the open sea and in estuaries. They can be found in Africa, India, Malaysia, Japan, Tahiti and the Phillipines.