To ensure the longevity of the fishing hobby in Australia each state has implemented systems that prevent people from taking more than their fair share of the fish/marine life and damaging the ecosystems that naturally replenish marine stocks.
Depending on your destination you may be required to obtain a recreational fishing licence. These licences are generally available from fishing authorities in the State or even online. Licences can range in validity from 2 days to 3 years depending on your requirements.
There are also restrictions in place regarding the number of fish/marine life you may take from the water and the minimum size these creatures must be for you to take them. As the fisher it is your responsibility to know the current restrictions in the area.