title: Radiological impact of the nuclear power plant accident on freshwater fish in Fukushima: An overview of monitoring results.
abstract: Radionuclide ((131)I, (134)Cs, and (137)Cs) concentrations of monitored freshwater fish species collected from different habitats (rivers, lakes, and culture ponds) in Fukushima Prefecture during March 2011-December 2014 (total 16 species, n = 2692) were analyzed to present a detailed description of radionuclide contamination after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, and to elucidate species-specific spatiotemporal declining trends of (137)Cs concentration for their respective habitats. Low concentrations of (131)I (≤24 Bq kg(-1)-wet) were detected from only 11 samples collected during March-June 2011, demonstrating that (131)I transferred to freshwater fish were not intense. In river and lake fishes, a more gradual decrease and higher radiocesium ((134)Cs, (137)Cs) concentrations were observed than in culture pond fishes, which strongly implied that radiocesium in freshwater fish species was mainly bioaccumulated through the food web in the wild. During 2011-2014, percentages above the Japanese regulatory limit of 100 Bq kg(-1)-wet for radiocesium in river and lake fish (14.0% and 39.6%, respectively) were higher than in monitored marine fish (9.9%), indicating longer-term contamination of freshwater fish species, especially in lakes. Higher radiocesium concentrations (maximum 18.7 kBq kg(-1)-wet in Oncorhynchus masou) were found in the northwestern areas from the FDNPP with higher deposition. However, radiocesium contamination levels were regarded as 1-2 orders of magnitude less than those after the Chernobyl accident. Lagged increase of (137)Cs concentration and longer ecological half-lives (Teco: 1.2-2.6 y in the central part of Fukushima Prefecture) were observed in carnivorous salmonids (O. masou, Salvelinus leucomaenis), whereas a rapid increase and decrease of (137)Cs concentration and shorter Teco (0.99 and 0.69 y) were found in herbivorous and planktivorous osmerids (Plecoglossus altivelis, Hypomesus nipponensis) with younger age at maturity. Comparison of Teco among salmonids, osmerids, and cyprinids suggests that, in addition to the fish feeding habits and life-cycles, hydraulic conditions in rivers and lakes (e.g., turnover time), which are expected to affect radiocesium concentration in prey items, are an important factor affecting the (137)Cs decreasing rate of freshwater fish.
authors.affiliation: Institute of Environmental Radioactivity at Fukushima University, Fukushima, Fukushima 960-1296, Japan. Electronic address: t-wada@ipc.fukushima-u.ac.jp.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Wada
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tomiya
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Enomoto
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sato
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Daigo
authors.initials: D
authors.lastname: Morishita
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Izumi
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Niizeki
authors.affiliation: Fukushima Prefectural Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Shunji
authors.initials: S
authors.lastname: Suzuki
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 Inland Water Fisheries Experimental Station, Inawashiro, Fukushima 969-3283, Japan.
authors.forename: Gyo
authors.initials: G
authors.lastname: Kawata
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism*; D005618:Fresh Water; D062406:Fukushima Nuclear Accident; D007457:Iodine Radioisotopes / Q000378:metabolism*; D007564:Japan; D055848:Nuclear Power Plants; D000069079:Radiation Exposure; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000378:metabolism*
chemical_list: D002588:Cesium Radioisotopes; D007457:Iodine Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: (131)I; (134)Cs and (137)Cs; Ecological half-life; Freshwater fish; Fukushima; Nuclear power plant accident