title: Effects of the nuclear disaster on marine products in Fukushima: An update after five years.
abstract: Original data (134Cs and137Cs, and sampling location) of marine products in Fukushima Prefecture monitored during 2011-2015 (n = 32,492) were analyzed to present an updated detailed description of radiocesium contamination after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident and to examine taxon/habitat-specific decreasing trends in different areas. Furthermore, marine species data presented by the Tokyo Electric Power Company (TEPCO) during 2012-2015 (n = 5458) were analyzed to evaluate the decreasing trends of137Cs inside and outside (within a 20 km radius) of the FDNPP port. Monitoring results by Fukushima Prefecture show that percentages of samples higher than the Japanese regulatory limit of 100 Bq kg-1-wet (>RL%) were higher, whereas those below the detection limit (<DL%) (mean 8.3 and 7.4 Bq kg-1-wet for134Cs and137Cs, respectively) were lower in demersal fishes than in pelagic fish or other taxa. However, >RL% and <DL% of demersal fish respectively decreased dramatically and increased gradually to 0.06% and 86.3% in 2015, although slightly elevated radiocesium concentrations were still observed in shallow areas south of the FDNPP. The drastic decrease in radioactivity was supported by the spatiotemporal distribution of radiocesium concentrations in demersal fish, in which higher concentrations that were frequently observed in 2011 and 2012 were rarely detected in 2015, even within the 20 km radius area (maximum 220 Bq kg-1-wet in Japanese rockfish Sebastes cheni). Statistical analyses of TEPCO data revealed that137Cs concentrations both inside and outside of the FDNPP port decreased exponentially with time: The respective geometric mean days of ecological half-lives were 218 d and 386 d. These results show clearly that the contamination level of marine products in Fukushima Prefecture, even within the 20 km radius area, has decreased drastically during the five years after the FDNPP accident, although137Cs concentrations higher than 10 kBq kg-1-wet were still detected in some specimens of sedentary rockfishes (S. cheni, Sebastes oblongus, and Sebastes pachycephalus) in the FDNPP port. Fishing operations started on a trial basis in June 2012 have gradually expanded the target areas and species. Careful monitoring should be continued to accelerate the restoration of coastal fisheries in Fukushima Prefecture.
authors.affiliation: Institute of Environmental Radioactivity, Fukushima University, Fukushima, Fukushima 960-1296, Japan; Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan. Electronic address: t-wada@ipc.fukushima-u.ac.jp.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Wada
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Fujita
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Nemoto
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Shimamura
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Takuji
authors.initials: T
authors.lastname: Mizuno
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Sohtome
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Kyoichi
authors.initials: K
authors.lastname: Kamiyama
authors.affiliation: Soma Branch, Fukushima Prefectural Fisheries Experimental Station, Soma, Fukushima 976-0022, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Narita
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Hatta
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ogata
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Takami
authors.initials: T
authors.lastname: Morita
authors.affiliation: Fukushima Prefectural Fisheries Experimental Station, Iwaki, Fukushima 970-0316, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Igarashi
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes / Q000032:analysis; D004190:Disasters; D017753:Ecosystem; D005399:Fishes / Q000378:metabolism; D062406:Fukushima Nuclear Accident; D006207:Half-Life; D011834:Radiation Monitoring; D014041:Tokyo; D014875:Water Pollutants, Radioactive / Q000032:analysis* / Q000378:metabolism
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Demersal fish; Ecological half-life; Fukushima; Marine products; Radiocesium