Radiocaesium elimination in fish: variation among and within species.
Ecotoxicological models are used to assess the effects of radionuclides on freshwater ecosystems and the potential transfer to humans depend on accurate laboratory estimates of the elimination rate of radionuclides in fish. The elimination rate (excretion) of caesium (134Cs) of Atlantic salmon, Salmo salar (two populations), Arctic charr, Salvelinus alpinus (two populations), whitefish, Coregonus lavaretus, and bream, Abramis brama, was estimated experimentally by single-dose caesium labelling and measures of subsequent samples of groups of fish maintained at different temperatures. Elimination rates between populations of the same species and among species were compared. Populations of the same species from similar thermal environments had similar elimination rates (Atlantic salmon) whereas those from different thermal environments differed significantly (Arctic charr). Caesium elimination rates varied among fish species. Bream had slower elimination rates than the other species at all temperatures, whereas Atlantic salmon had quicker elimination rates than the others at 16°C. The remaining differences among species were not consistent across temperatures, indicating differences in thermal performance. Approximately 45% of the estimated elimination rates differed significantly from those predicted by a general caesium elimination model. It is concluded that a single model for caesium elimination, valid for a wide range of species and populations, may be difficult to attain.