Lots of confusion here – not surprising as many Australians are also confused by the terminology.
Australia's crayfish/lobsters can basically be categorised into freshwater and seawater species.
The freshwater species all look quite similar but range in size from a couple of centimetres to the giant Tasmanian species which can weigh in at over two kilograms. The appearance of these species with their large claws is somewhat similar to the marine lobster of North American and European waters, however these are actually all crayfish.
The marron ( same spelling for singular and plural ) is a native south-western Australian species of freshwater crayfish. It can be cultivated in dams and there is a small aquaculture industry built about it. They have a sweeter taste and are preferred by some people to the marine lobster/crayfish.
The wickedly overpriced marine crayfish/lobsters are neither crayfish nor true lobsters. Traditionally called crayfish by the locals, the name was changed ( in the face of some antagonism ) to Rock Lobster to market them first to the Japanese market and more recently to the Chinese. They are actually spiny lobsters and lack the large claws of the northern hemisphere true lobsters. The industry is very tightly regulated – to protect the stocks – and prices paid overseas very high, hence the ridiculous price which puts them out of reach of most Australians. They are now most commonly marketed as Southern Rock Lobster.
The superficially similar spiny lobsters of northern Australian waters are badly behaved ( they don't readily go into traps ) and most are caught by divers. As a result the industry around these is small.
I trust that this adds to the confusion. My only excuse is that I didn't have anything else to do. Well I do but it's hot outside and in the workshop – 33 degrees C today. Must go, I think the dogs are destroying the lounge room.
Keep well
Pero