Hi Pearlfan,
I think seawater or saltwater is often used instead of Akoya because of a bias against Akoya pearls which has been obvious to me for sometime now. Just my opinion
But so many Akoya cultured pearls seem to have so thin a nacre coating and have been left in the sea for so little time that in at least some quarters it seems an insult to call a pearl an Akoya. I realise there are many good Akoya pearls but there are also some very inferior ones sold, especially on eBay. I think this is the reason many people tend to steer clear of the team Akoya.
I am not an expert by any means and hope one of those chimes in here with more help for you. I do realise that Akoya are cultured in both Japan and China but I think most of the public think they are only cultured in Japan.
Nice to meet you. Are you a seller/supplier ? because I am looking for a good Chinese supplier
Bodecia