title: Exposure of a herbivorous fish to ¹³⁴Cs and ¹³⁷Cs from the riverbed following the Fukushima disaster.
abstract: Ayu Plecoglossus altivelis, a herbivorous fish, is an important fishery resource and key component of the foodweb in many Japanese streams. Radionuclide contamination of this species is likely transferred to higher trophic levels, include humans, in the food chain. After the Fukushima accident in March 2011, ayu were exposed to highly contaminated silt while feeding on algae attached to the riverbed stones. To understand the route by which herbivorous fish are exposed to radionuclides, the activity concentrations of sum of (134)Cs and (137)Cs (radiocesium) were analyzed in riverbed samples (algae and silt) and in the internal organs and the muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. Although there was a positive correlation between the radiocesium activity concentrations in the muscle and the internal organs of ayu, the median activity concentration in the muscle was much lower than those in the internal organs. The activity concentrations of radiocesium in the riverbed samples and the internal organs and the muscle of ayu were correlated with contamination levels in soil samples taken from the watershed upstream of the sample sites. The results of the generalized linear mixed models suggest that the activity concentrations in both the internal organs and the muscle of ayu declined over time. Additionally, the activity concentrations in the internal organs were correlated with those in the riverbed samples that were collected around the same time as the ayu. The activity concentrations in the muscle were correlated with ayu body size. Our results suggest that ayu ingest (134)Cs and (137)Cs while grazing silt and algae from the riverbed, and a part of the (134)Cs and (137)Cs is assimilated into the muscle of the fish.
authors.affiliation: National Research Institute of Aquaculture, Fisheries Research Agency, Nikko, Tochigi 321-1661, Japan. Electronic address: tsuboi118@affrc.go.jp.
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Tsuboi
authors.affiliation: Japan Sea National Fisheries Research Institute, Fisheries Research Agency, Suido-cho, Chuo-ku, Niigata 951-8121, Japan.
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Abe
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Fujimoto
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Kaeriyama
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ambe
authors.affiliation: National Research Institute of Aquaculture, Fisheries Research Agency, Nikko, Tochigi 321-1661, Japan.
authors.forename: Keishi
authors.initials: K
authors.lastname: Matsuda
authors.affiliation: Fukushima Prefectural Inland Fishery Institute, Nagata-Higashinakamaru, Inawashiro, Yama, Fukushima 969-3283, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Enomoto
authors.affiliation: Fukushima Prefectural Inland Fishery Institute, Nagata-Higashinakamaru, Inawashiro, Yama, Fukushima 969-3283, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tomiya
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Takami
authors.initials: T
authors.lastname: Morita
authors.affiliation: National Research Institute of Fisheries Science, Fisheries Research Agency, Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Ono
authors.affiliation: National Research Institute of Aquaculture, Fisheries Research Agency, Nikko, Tochigi 321-1661, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Nagasaki University, Bunkyo-machi, Nagasaki, Nagasaki 852-8521, Japan.
authors.forename: Kei'ichiro
authors.initials: K
authors.lastname: Iguchi
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes / Q000032:analysis / Q000378:metabolism*; D062406:Fukushima Nuclear Accident; D019015:Geologic Sediments / Q000032:analysis; D007564:Japan; D036441:Osmeriformes / Q000378:metabolism*; D011834:Radiation Monitoring; D045483:Rivers / Q000737:chemistry; D014018:Tissue Distribution; D014875:Water Pollutants, Radioactive / Q000032:analysis / Q000378:metabolism*
chemical_list: D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive
keywords: Ayu; Bioaccumulation; Nuclear accident; Radioactive cesium; Radioecology; Soil contamination