There are a number of activities impacting on aquatic habitats and species for which you need a permit.
NSW DPI maintains a list of fish species which cannot be imported (live) into NSW without a specific permit. These are species which have been identified as potentially posing a significant threat to native wildlife, ecosystems, human health or the State's aquaculture industries. See here for the current list. AQIS rules and regulations apply to the importation of fish from overseas.