To fish in Sydney you generally need to have a license from the NSW Fisheries Department unless you are younger than 18 years. Licenses are about $25 a year. Equipped with your license, you can catch and keep almost anything. For game fish there are size limits (too small, let it go) and bag limits (maximum number of each species per person per day). You can go anywhere except for specific protected areas. In Sydney there are several Intertidal Protected Zones. You can fish with a line from some of these, but can't collect anything from the rock shelves or pools. There is an aquatic reserve that contains most of the Northern arm of Sydney Harbour. This is a no fishing zone. Nationally, there are only 10 protected marine species in Australia. These are unlikely to be found in Sydney, with the exception of the weedy sea dragon (a sea horse).