Impact of the Great East Japan Earthquake on Reproductive Biology ofthe Freshwater Teleost Bluegill Lepomis macrochirus

摘要

Soon after the Great East Japan Earthquake and the subsequent accident at the Fukushima Daiichi nuclearpower plant, we studied the reproductive biology of freshwater teleost bluegill (Lepomis macrochirus) in a pond in thecity of Iwaki, Fukushima Prefecture, about 50 km south of the nuclear power plant. The breeding period of the bluegillwas abbreviated and the frequency of spawning decreased. The radiation air dose rate and level of radioactivity in the fishwere less than would be expected to trigger behavioural alterations or to suppress reproduction. The occurrence of aftershocksand two episodes of torrential rain is the likely reason for changes in the reproductive behaviour of bluegill in thepond. These results suggest that our observations can be explained by a combination of natural disasters, rather than theeffects of nuclear radiation.