Bioaccumulation of 137Cs and 85Sr by an Australian sub-tropical freshwater teleost (Bidyanus bidyanus)

Adult Silver Perch (Bidyanus bidyanus) were exposed to 137Cs and 85Sr for 8 weeks to determine radionuclide concentration factors (CFs) for use in a dose assessment model database for sub-tropical and tropical ecosystems. At equilibrium, the fresh weight CFs for 137Cs and 85Sr in the flesh of B. bidyanus were 12.6 ± 5.2 kg 1−1 (mean ± S.E.) and 0.73 ± 0.21 kg 1−1, respectively. The mean CFs were considerably lower than those expected for temperate freshwater fish, but were consistent with recently reported values for other sub-tropical and tropical freshwater fish. The results indicate that the use of recommended CFs for radiological dose assessment models, based on temperate freshwater fish, may provide overestimates of dose when applied to sub-tropical and tropical fish. The biological half-lives of 137Cs (19 ± 2 days) and 85Sr (5 ± 1 days) in the flesh of B. bidyanus, estimated from a one-compartment exponential uptake model, were lower than reported values for four other species of sub-tropical and tropical freshwater fish. Cesium-137 was distributed in B. bidyanus as follows: flesh (63%) > skin/scales (22%) > bone (15%). Conversely, 85Sr showed similar activities in the bone and skin/scales that were still increasing after eight weeks, while the levels in the flesh remained relatively low. Analysis of the skin/scales component showed that the majority of 85Sr (∼ 94%) was located in the scales.