Great effort. You are correct. The fish is a juvenile dusky Morwong and is also known as butterfish. As they get older they seem to lose the spots on the tail.
In the future you'll start targeting his/hers relatives - Magpie perch, Red Morwong, Banded Morwong, Blue Morwong, Queen Snapper and Jackass. Which are all obtainable in Vic and are far better eating.
Great work with the float. Make sure you can attach your catch bag to your float. Dont have the bag attached to your waist with fish in it. You will be harassed by rays and seven gills or something bigger that might think your part of the food chain. Catch bag can also be used to hold items like Abalone knife, bottle of water, etc
There is also a good vid on the site which goes for bout 10mins that shows you common fish you will encounter. Good if you are still learning your fish species. There is also a good list of fish and they're eating qualities put together by the likes of Rhino, Brett and others. I highly recommend going through these.
Hope to see more reports and now you definitely know gun shoots straight.
Good shooting
Geoff