The fish your describing are native species, the fact that they may be around what you would call not usual habit just a part of evolution. Species move following food or warmer currents.
https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:43e13442-afd0-443b-96fb-9a462eeea542
The day I can catch Coral trout in Sydney I will rejoice & probably go out & buy a bottle of Penfolds Grange to enjoy with if for dinner π
But your right in that if you do catch a species like carp then I believe its against the law to actually return it, & if its some unusual or foreign species then report it to the DPI or equivalent body.
Id be more worried about the crown of thorns star fish consuming the Great Barrier Reef or the cane toads reaching Sydney, also the effects on the country from introduced feral species like pigs, foxes. cats, dogs, goats, rabbits, deer.
And I certainly wont be donating any money to some Tsethar Buddhist group, Id rather donate to our farmers or another needy Australian charity where it will actually have a good effect for us!