A species of shellfish, Thais clavigera, has disappeared in a 30km coastal area near Japan's crippled Fukushima nuclear plant, Japanese experts said.
Researchers from Japan's National Institute for Environmental Studies and National Institute of Radiological Sciences conducted the study in April 2012 on the shellfish's living status in 43 places from Japan's Chiba to Iwate prefectures for four months, Xinhua reported.
The team found that the Thais clavigera was extinct in eight of 10 places within the 20km radius alert zone of the nuclear plant.
The plant was damaged by a tsunami in March 2011 and triggered the world's worst nuclear disaster since Chernobyl in 1986.
Other shellfish species such as Cellana grata were found in the alert zone but their numbers had declined. A high dose of radioactive materials were found inside their bodies, the researchers said.
Thais clavigera, a kind of shellfish that widely lives across Japan, was found in most places that had been surveyed, including 25 of 33 places outside the alert zone, they said.
Toshihiro Horiguchi, the head of the team, said it was a rare occurrence that Thais clavigera entirely disappeared from a 30km long area, adding that the extinction was probably caused by the nuclear crisis.
The link between the disappearance and the catastrophic tsunami was excluded as the shell was also found in other areas that affected by the disaster, the team said.
The report was announced in an annual meeting of the Japanese Society of Fisheries Science.