Juat called AVA and spoke to a friendly gentleman. Clams is under Cites species, so you need a cites import and export permit from AVA. Dont be confused with the import licence, which is needed only if you bring in more than the stipulated allowable quantity.
The good part is soft corals is not in cites list. Fish except koi and carps is also not in the cites list. So you can hand carry them within the lawful stated quantity.
cheers,
** In short, if you hand carry a clam, you will need only a Cites Permit from AVA. If you want to bring in 100 clams, you need a Cites Permit and an import licence from AVA.**