Press Release

December 4, 2012

Incorporated Administrative Agency, Fisheries Research Agency

On the project “Urgent study on the sources and routes of high-level radioactive cesium contamination in fish” funded by the Strategic Funds for the Promotion of Science and Technology

The Fisheries Agency has been entrusted to carry out a project entitled “Urgent study on the sources and routes of high-level radioactive cesium contamination in fish,” which is a part of the Strategic Funds for the Promotion of Science and Technology, and is working jointly with the Institute of Industrial Science and the Graduate School of Agricultural and Life Sciences of the University of Tokyo, National Maritime Research Institute, Forestry and Forest Products Research Institute, and the prefectural government of Tochigi.

The project aims to quickly identify the sources and routes of radioactive cesium contamination in fish under the leadership of the Council for Science and Technology Policy by gathering all technologies of the participating institutes, contribute to both regaining trust in the safety of marine products and preventing risks of harmful rumors, optimize methods of monitoring marine products and their habitats toward future resumption of fisheries, and contribute to rational setting (or removal) of shipment restrictions.

The project has been underway since November 29, 2012, and is scheduled to end in March 2013.

Objectives and background of the project
  • Although the cesium level in marine products is decreasing as a whole, fishermen in and near Fukushima Prefecture are still suffering from harmful rumors and fishing restrictions.
  • The Basic Plan for Fisheries, which was decided by the Cabinet in March 2012, also states that related ministries and agencies are to comprehensively, systematically and jointly tackle clearing up consumers’ uneasiness and prevent risks of harmful rumors. The Fisheries Agency is publishing information such as the contamination levels monitored in marine products on its webpage, etc. to help consumers have correct knowledge and understanding and has held (about 40) explanatory meetings with consumers’ organizations, etc.
  • With such a background, the highest level (25,800 Bq/kg-wet) of all marine products was detected in fat greenling (Hexagrammos otakii) in August 2012. The levels in freshwater fish are also high, revealing unexpectedly prolonged contamination. If the causes were to remain obscure, consumers would probably keep feeling unsafe about aquatic products on the market.
  • Lack of knowledge also hinders restoration of the fishing industry because fishermen, who want to restart fishing as early as possible, cannot get a rough idea of when the contamination will fall to a level that they can restart fishing.
  • Early dispatch of information effectively clears up consumers’ uneasiness. The causes should also be urgently investigated to correctly assess the effects of movements of contamination sources, etc. to carry out effective surveys.
Contents of the project

The research institutes and universities are carrying out the following researches using the Strategic Funds for the Promotion of Science and Technology.

  • Technologies are being investigated to analyze the distribution of radioactive substances in the otoliths of high-level contaminated fat greenling, etc. The data of radioactive distribution is being analyzed together with the Sr/Ca and stable isotope ratios in the otoliths to estimate when and where the highly contaminated fish were exposed to the high-level radioactive substances. (Fisheries Research Agency)
  • Relatively high cesium levels have been detected in fish that inhabit brackish waters, such as black sea bream (Acanthopagrus schlegelii). Fish culture experiments are being conducted by feeding fish species that inhabit brackish waters with feed containing large amounts of cesium and potassium, which behaves similarly to cesium. Multiple immunofluorescence staining has been conducted to identify chloride cells, which excretes cesium and potassium. Fish are also reared in conditions of different potassium concentrations, and the effects of potassium concentrations in the water and feed on the activity of the chloride cells are investigated to understand the mechanisms of high radioactive cesium level in black seabream and other brackish water species. (Graduate School of Agricultural and Life Sciences of the University of Tokyo)
  • To identify the transport properties, such as fields of activities, of fish that inhabit highly contaminated areas, fish are being marked and recaptured, and/or are biologged. (Fisheries Research Agency)
  • A tow-type measuring system is being constructed to measure the cesium level in the sea bed continuously over a large area. The system will be used to measure radioactive cesium in the sea bed in areas that have been little monitored, such as within 20 km of Fukushima Dai-ichi Nuclear Plant, find hot spots of radioactive cesium, and quantify the level of the hot spot, if any (Institute of Industrial Science of the University of Tokyo and National Maritime Research Institute). For this project, the Fisheries Research Agency has conducted a survey on a research vessel “Soyo-maru” (December 7 to 12).
  • Using Lake Chuzenji, where the level of radioactive cesium in the fish is relatively high, as the reference and setting nearby rivers and lakes where the levels are low as water models, the distribution of radioactive cesium in nearby forests and along streams is being investigated. Fish and their bait organisms are collected and subjected to radioactive cesium level measurement and stable isotope analysis to understand the characteristics of radioactive cesium level in the food chain, which is connected to highly contaminated fish, and in the organisms that constitute the food chain. Non-contaminated fish are reared in nets in Lake Chuzenji and nearby waters, released to the environment, and periodically checked for contamination level to investigate whether they are continuously contaminated or not and how fast radioactive cesium accumulates (Fisheries Research Agency, Forestry and Forest Products Research Institute, and the prefectural government of Tochigi).
Scheduled uses of the study results

The knowledge obtained by this project will be reported to the Ministry of Agriculture, Fisheries and Forestry and other related ministries and agencies, published on the web and in meetings, and used to help regaining trust of consumers on aquatic products on the market and preventing harmful rumors.

  • Precise knowledge on seabed contamination will contribute to optimizing methods for monitoring contamination levels in marine products and their habitats and to restarting fishing.
  • Identification of species, sea areas and rivers that are prone to high contamination will contribute to rational setting or removal of shipping restrictions.
Budgets
  • 1) 130 million yen for identifying the sources and routes of high cesium levels monitored in marine fish
  • 2) 60 million yen for identifying the sources and routes of high cesium levels monitored in freshwater fish
(Entrusted by the Fisheries Agency)