I sincerely hope they aren't here and nobody tries to sneak them in. The American species (specifically including Procambarus clarkii) are resistant carriers of the "Crayfish disease" which nearly wiped out freshwater crayfish in Europe when it arrived there. Here in Australia we have the most diverse and interesting freshwater crayfish fauna on earth, including some dwarf crays that have more potential for line-breeding colour forms (purple, black, blue, red etc) than wild P. clarkii ever did. Our crays have been confirmed to also be highly susceptible to the disease - it is possible that our amazing native freshwater crabs and shrimp are equally as susceptible. Fear of this disease impacting the economically important crustacean industry is why no exotic shrimp have been approved for legal importation here and probably none ever will be. If you think the authorities are tough on the shrimp hobby now, wait and see how they are if the New World crays start to show up. Don't expect there to be a hobby surviving here for very long. I would be in full support of any tank of Procambarus in Australia to be nuked by fisheries. Don't tell me if you've got them.