NIFS said  shellfish harvesting ban was reissued as paralytic shellfish toxins in the wild mussels from the nearshore waters of Changwon, Gyeongsangnam-do and some sea areas of Saha-gu, Busan are in excess of permissible paralytic shellfish poison (PSP) level (0.8㎎/㎏). 

In a real-time survey that NIFS and Gyeongnam Fisheries Safety and Technology Institute conducted under the shellfish toxins management plan, the water sampling yielded less than the permissible PSP level for two consecutive weeks, extending into the ban being fully lifted in all surveyed coastal areas as of May 26. 

However, on May 28 -shortly after the ban was lifted- paralytic shellfish toxins in mussels from Deokdong and Okgye-ri, Changwon once again exceeded the permissible level; a subsequent survey on June 1 detected the toxins as far as the coastal waters of Napo-ri, Changwon, and Dadae, Busan, indicating an expansion of the affected area where the toxins level (0.86~2.33㎎/㎏) exceeded the permissible PSP level. 

To identify the cause of toxin reoccurrence, NIFS analyzed the DNA of causative plankton and found that there was a change in the plankton species. Alexandrium catenella, a traditional toxin-producing phytoplankton, proliferates between 15℃ and 20℃, but the analysis indicates that the recent rise in water temperature to over 20℃ has led to an increase in the density of Alexandrium pacificum*, thereby causing a renewed increase in shellfish toxins concentration. 

*Alexandrium pacificum exhibiting optimal growth between 20℃ and 25℃

“There have been similar cases in the past that shellfish harvesting ban was reissued after it was fully lifted due to shellfish toxins being detected again. As the levels of shellfish toxins have exceeded the permissible limit once again, NIFS will maintain its monitoring system at least once a week to ensure there are no gaps in safety management,” said Kwon Soon-wook, the President of NIFS.