The Death of Akoya Oysters in Japan and What it Means for You

Published On: 
October 16, 2019
Japanese Akoya tokyo japan spats

The Death of Akoya Oysters in Japan


Being the bearer of bad news is never an easy task.  However, we at Amit Trading would like to inform all of our customers, friends, and readers about what is exactly happening here on the ground in Japan.  A large amount of unexplained deaths is occurring in the oyster population.  This is extremely important news because over 90% of the world’s Akoya Pearls come from three main areas in Japan.  We are sure that you may have a lot of questions starting with:

  1. What exactly is happening?
  2. What are the effects?
  3. Where is it happening?
  4. Why is it happening?
  5. Has this happened before
  6. How will the sudden death of a substantial amount of Akoya oysters affect buyers and suppliers.
  7. What should I do?

 In this blog we will briefly look at how the oysters are being affected, which areas are affected, as well as some possible theories to the reasons for what is occurring.  We will end with some advice from a voice that carries over half a century of experience in the saltwater pearl industry.


A mysterious phenomenon of unknown origin is affecting the Akoya pearl oysters here in Japan.  Life for the Pinctada Fucata oysters, as they are known in the scientific community, begins after fertilization.  Afterwards, in larvae form, they gain the ability to swim until settling down into their spat or juvenile form.  The entire process takes around 2 to 2 ½ weeks in total.

For reasons currently unknown, in Japan an illness is affecting the oysters and causing them to die in droves. Deaths are being reported for oysters in the larvae, juvenile/spat, and mature stage.

Pearl And Diamond Jewelry By, Tokyo, Japan


Pearl And Diamond Jewelry By, Tokyo, Japan

Credit: CSIRO Marine Research


While the larvae are dying, the juvenile oysters are where farmers are really noticing the effects of the mysterious disease.  The mantle, the oyster’s skin, is weakening and there is some discoloration.  Instead of a milky white color of a healthy oyster, the tint is a much darker tone with a shriveled look.  The mantle is really important for forming the shell around the oyster for protection. The mantle also plays a part in the oyster production of nacre (mother of pearl).  Unfortunately, something is causing deformities in the Akoya oysters’ mantles and causing them to weaken or die.  There is also discoloration from a milky white color to a much darker tint.  Consequently, the damaged oyster cannot protect itself nor form the desired lustrous white pearls it is famous for.  The end result is death for the pearl oyster.

Pearl And Diamond Jewelry By, Tokyo, Japan

Credit: CSIRO Marine Research


If you are wearing an Akoya Pearl, chances are that it came from one of three places, Ago Bay in the Mie Prefecture, Omura Bay in Nagasaki Prefecture, or Uwajima City in Ehime Prefecture.  These are the top three areas for “pearl production that provide the world with 95% of the world’s Akoyas.  In order of production Ehime ranks number first while second and third are held respectively by Nagasaki and Mie” (Causes of Pearl-Cultured).

Pearl And Diamond Jewelry By, Tokyo, Japan



Nestled in Western Japan, this is known at the birthplace of the Akoya Pearls.  Koichi Mikimoto, the pioneer of pearls, would develop the saltwater Akoyas and start seeing mass success in the early 1920s.  However, this area has been hit extremely hard by the epidemic in the last few weeks.

252 companies were surveyed with 120 reporting substantial losses in the area of 20%.  Some fear that the deaths may be much higher since only 48% have responded. Around “70% or 1.7 of the 1-year oyster juveniles have died.  23% or 300,000 of the 2nd year juvenile oysters have died, with 25% of the 3-year oysters dying out.” (More than 2 Million Pearl Oysters).

Pearl And Diamond Jewelry By, Tokyo, Japan



Located in Southern Japan, Nagasaki is Japan’s 2nd largest area for pearl production.  It currently produces around 7 tons of pearls annually in Japan.  Unfortunately, around 35% of the juvenile oysters were reported dead from a government survey from 29 major companies.  Not everyone has been so lucky with some farmers losing as much as 80% of their larvae.  The silver lining is that not many of the mature pearls were affected (NHK News).

Pearl And Diamond Jewelry By, Tokyo, Japan



Located on the Smaller island of Shikoku, Ehime has been “the leader in Akoya pearl production.  The area has been responsible for producing 7664kgs of pearls yearly”.  Since the later half of July, many farmers have noticed that the number of deaths were higher than average along the coastline.  The places that were hit the hardest were the areas from Uwajima City to Ainan town.  “Of the 300 contractors that were surveyed, over 80% reported deaths” (Causes of Pear-Cultured Pearl Oyster).

Pearl And Diamond Jewelry By, Tokyo, Japan

Credit: Lincun


  There are a few theories, but the investigation is ongoing at the moment.  Some researchers feel that bacteria or virus is the cause while others feel that global warming or climate change is the culprit.  In the late 90s and early 2000s, there has been a large amount of Akoya deaths.  The incidents were later dubbed the “Akoya Virus.  The symptoms from the past and today are eerily similar.  A weak or damaged mantle that prevents the pearl oyster from closing completely.  In the past the “mantle was a reddish color,” but now there haven’t been many with the color red.  (Causes of Pearl-Cultured Pearl Oyster).

Pearl And Diamond Jewelry By, Tokyo, Japan



Rising water temperatures are currently being investigated in Ago Bay, Mie.  A recent investigation discovered a rise in the temperature that was “2.5 times higher than the 15-year average”.  The large number of casualties are causing a huge increase in the temperature of the sea.  This causes an increase in activity for the oysters.  Activity requires fuel in the form of phytoplankton.   A shortage has also been noticed which means a lack of necessary nutrients.  Some scientist feel that this lack of nutrition makes the oysters more suspectable to foreign agents.  Also, without the right amount of fuel, the oysters cannot grow to their full potential or completely form their mother of pearl.  This could point to why the larvae and juvenile are much more affected than the mature oysters (Massive Death of pearl oysters).

Pearl And Diamond Jewelry By, Tokyo, Japan



The desired effect is not to create any scares but only look at any past events, present situations, imperical data and attempt to make sound predictions.  As with the law of supply and demand, a lower supply of Akoyas could result in a slight increase or huge increase in the price (Canedy).  Please remember that the mature oysters are the least affected by the current disease.  This means that the current supply is least likely not be affected.  However, future supplies are really dependent on how soon scientist can discover the root cause and prevent future outbreaks.  Mature Oysters can produce pearls for 3 years at the maximum.  Juvenile spats usually need 1 to 2 years to mature so there might be a slight increase.   The governments in certain areas have already started conducting countermeasures such as “breeding larvae artificially in protected areas to increase the juvenile population” (Causes of Pearl-Cultured Pearl).  Initially they were areas such as “Uwajima City selling the new juvenile larvae in order to increase the production.  However, the policy has changed to giving them to the farmers free of charge” (The First Pearl Oyster).  One ray of hope is that the governments of these regions have been fast acting and are making an earnest effort to find the root cause and preserve the Akoya pearl industry in their respective areas.


“Causes of Pearl-Culture Pearl Oyster” Sep. 4. 2019.  NHK New via The         Teller Report. Oct. 11. 2019 (website)

Canedy, Dana. “Mysterious Virus At Source Drives Up the Price Of Pearls”

The New York Times.  May. 24. 1998 (website)

“In Ehime and Mie Prefecture” Sep. 5. 2019. NHK News via The Teller Report. Oct 11. 2019

“Massive Death of Pearl Oysters” Sep. 13. 2019. NHK News via The Teller Report.  Oct. 11. 2019 (website)

 “More than 2 Million Pearl Oysters” Sep. 9. 2019. NHK News via The Teller Report. Oct.11. 2019 (website)

 “Pearl oyster mass death Nagasaki Prefecture” Sep. 9. 2019. NHK News via The Teller Report. Oct.11. 2019 (website)

“The first pearl oyster shellfish used for pearl” Oct. 2. 2019. NHK News via The Teller Report. Oct. 11. 2019

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