They are different. The Australian crayfish is actually a rock lobster. Rock lobsters are also known as crawfish, langouste
and spiny lobster. They are served as lobster in Australia and also around the Mediterranean. Although they have only small claws with not much meat, the fine white body meat is excellent and there is a good proportion of it in comparison to total weight. They are commonly sold at about 2 kg weight; you should allow 600-700 g shell-on weight per person.
Crayfish, on the other hand, are small freshwater crustaceans found in Britain, Scandinavia and in the bayous of Louisiana, where they feature in Cajun cooking. In most recipes, large shrimps or yabbies can be substituted with freshwater crayfish.
** Asian Online Recipes