A government sponsored breading program,something along the lines of what is done in the United States where certain fish are bred and released in the wild when they get a certain size.The private farms already have the know how and a few of them could be paid to carry out this task and fishing for theses Arowana would have to be guarded against by forest rangers or a similar entity.
I don't care if the Arowana never become available to American hobbyists but it would be unfortunate if they are wiped out,especially if they could have been saved.