Japanese Akoya Mortality


Nov 28, 2005
Hi Everyone,

I am surprised (or maybe I've just missed it), that there is no recent mention of the huge issue of the deaths of juvenile Akoya oysters here on the guide.
Is anyone following this matter and is there any recent news on this important issue that threatens to wreak havoc with the Akoya pearl trade?

I for one, sincerely hope that it can be brought under control and the cause dealt with as soon as possible.
Hi teeuk

I have not really heard of this happening at the moment...but in Japan's Akoya pearl farming -from my perspective- we don't have to wonder WHY are these mortalities happening; the question should rather be oriented towards WHEN will the next mortality occur???
And there are many, many reasons as to these mortalities continue to happen.

Thanks for your response.
I'd heard from a couple of sources that this started to be reported around September 2019, but perhaps because of the Pandemic appearing not long after, the news of this has not spread as much as it would have done in "normal" times.

Basically, it seems there were very big losses in the number of juvenile spat and no one seems to know the cause for sure.Some put it down to a new virus (somewhat ironically), while others believe climate change to be the cause.
The results of this will obviously soon come home to roost with production yields likely to be hit hard in the near future am very sorry to say.

There are a few references to it on the web, one of which is this: https://thesouthseapearl.com/blogs/n...xplicably-died

I came here looking for more up to date, information and was very surprised not to find any reference to it.

I truly hope that this situation is rectified very soon!
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When I was working on an akoya farm in Vietnam a couple of years ago mortality rates were a growing concern and the cause was that the sea was simply too hot. Oysters have a very narrow envelope for survival. they do not adapt. They just die.
The cure will be either finding a way to breed more temperature tolerant oysters of the same species, move the farms to cooler waters or move the farm ranks to cooler/deeper waters.
I am no expert on this, but this topic does remind me of the abnormal extreme weather caused by climate change in many places all over the world during the past year(s?). There are hot places that suddenly got very cold, cool places that got extremely hot unexpectedly, and not-wet places that rained heavily and continuously and flooded. Not sure if this happened to Japan but climate change is my main guess...
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I will quote some text from the article:

"As for possible factors for the mass fatalities, a Mie prefectural government study in September cited higher than usual seawater temperatures during the first months of this year, as well as a paucity of plankton that shellfish feed on.
However, prefectural officials have yet to reach a definitive conclusion. Such factors “may have contributed to the widespread deaths, but they are not the true cause,” a prefectural official said.
Scientists at the National Research Institute of Aquaculture in Minami-Ise, Mie Prefecture, suspected a possible infection of a transmitted disease among the shellfish, but none has been confirmed."

And this is the same story we have heard back in the 2010's, 1990's, 1980's...it is the same story, and the same explanation every time and I believe it is a case of the ostrich placing its head in a hole. The reality is that this is multi factorial problem, there are many "bunions" to step on and there are economic realities as well (policies and politics) at stake, smother with some pollution problems (fish farms produce a lot of waste!), the fact that the bays are not that open and there is little recirculation, add some increased temperatures (bacteria will flourish and consume Oxygen) and voila! You have another unexplained disaster!

In reality: Japan's Akoya pearl farming industry must change quite a bit to ensure its survival, but it must make a "reality check" and then elaborate strategies that will lead them into a true revival. In the meantime: we will listen about these massive mortalities every so many years.