Wednesday, September 14, 2016

Crab Die-Off in Kyushu

What is causing the die-off of crabs in northern Kyushu Japan? Could it be related to the unprecedented geological activity in that region in March and April of 2016?

Last spring there were over 1,000 earthquakes on the Japanese Island of Kyushu. Two of those quakes were quite large and caused severe damage and landslides in some areas, leading to public concerns about the safety of nuclear power plants in the region.

Japanese authorities reported that the nuclear plants were not impacted. Here is an image from Google maps of the plants that could have been impacted given their locations:

Below find the image of the location of the reported die-off of horseshoe crabs. The official cause is reported as "mysterious" :

The article below describing the crabs' demise explains that possible causes include changing sea levels, shortages of places to lay eggs, and lack of nutrition. An increase in water temperature has been ruled out:
TAKUYA MIYANO Hundreds of horseshoe crabs mysteriously die in Kita-Kyushu. The Asahi Shimbun, September 14, 2016,

KITA-KYUSHU--Nearly 500 dead horseshoe crabs have washed ashore at a tidal flat here, and researchers have no idea what is killing the endangered species that dates back 200 million years. According to a local horseshoe crab protection group, 50 to 60 dead horseshoe crabs are found annually at the Sonehigata tidal flat, one of the largest habitats of horseshoe crabs in Japan. But 490--the largest number over the last 20 years--have already been discovered this year...

...Satoshi Morinobu, a researcher at the Kasaoka Horseshoe Crab Museum in Kasaoka, Okayama Prefecture, said the creatures need much time to grow into adults, so the large number of deaths could deal a heavy blow.  
According to the Fukuoka Fisheries and Marine Technology Research Center, the seawater temperature off Fukuoka Prefecture in the summer was 1 degree higher than usual. But Morinobu said, “Horseshoe crabs can be found in further southern waters as well, so they must be resistant to high water temperatures.”
After the handling of contaminated water in Fukushima, I just have to wonder whether the crabs' death is related to problems at these plants. I hope someone tests them for radioisotopes.


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