Another fish contaminated with radiation was caught in waters off Japan's Fukushima Prefecture earlier this month.
Japan's Asahi Shimbun reported Tuesday the black rockfish had two.seven times above the permitted levels of radioactive caesium.
The latest finding also comes just a week after Tokyo dropped the bombshell that it is going to dump Fukushima wastewater into the ocean.
Reaffirming Seoul's opposition to the decision, South Korea's foreign ministry said Tuesday it will address Tokyo's decision through multilateral channels including the International Atomic Energy Agency, United Nations and World Health Organization.
The ministry added that it will actively pour all efforts into making sure there can be scientific and objective verification which is convincing to the international community.
And clarifying Seoul's stance, foreign minister Chung Eui-yong once again urged that Tokyo should present scientific evidence that guarantees the health and safety of the Korean people. adding that in future it should consult Seoul in advance.
FM Chung also made it clear that experts from Seoul should be able to participate in the IAEA's safety verification process.
Also in Tuesday's parliamentary session, Chung said that Seoul is still reviewing whether to take Japan back to the International Tribunal for the Law of the Sea.
While other countries including China, Russia and Singapore have also voiced deep concerns, the release is expected to be a big blow to neighboring countries including Taiwan's big fishing industry in Keelung city.
Noting that the U.S. is the only country in favor of the disposal, Chung said Seoul has asked Washington to clarify and to present scientific evidence regarding its claims that Tokyo's decision was made in a transparent way.
Washington is yet to give a clear response.
Kim Dami, Arirang News.