The origin of ¹³⁷Cs contamination, contamination levels, and its effective ecological half-life can differ among fish species, but until recently it was unknown whether interspecific differences in radiocaesium metabolism existed. We compare the trophic transfer of ¹³⁷Cs in five salmonid species under controlled conditions. Fish were fed a diet containing 200 Bq kg⁻¹ wet wt concentration of ¹³⁷Cs for a fixed period of time. While there were almost no differences in contamination levels among individual fish within a species during fixed periods, the rate of ¹³⁷Cs uptake was statistically different among the species examined, for which the effective half-life of ¹³⁷Cs ranged 49–84 days. No significant difference in rate of decline in the quantity of ¹³⁷Cs was apparent among species in two experiments after correcting for differences in growth. The effective half-life was shortest in Oncorhynchus mykiss and O. masou—two species exhibiting the best growth rate in both experiments—indicating an influence of the dilution effect associated with growth. When continuously fed 200 Bq kg⁻¹ wet wt concentration of ¹³⁷Cs for a period of 209–294 days, contamination levels in the five species ranged 216–240 Bq kg⁻¹ wet wt, and reached a steady state value. Our results indicate metabolic rate, although accompanying a change of body size, did not affect ¹³⁷Cs contamination levels in fish, which implies that contamination levels in the diet strongly determined contamination levels in fish.

¹³⁷ Cs污染的起源，污染水平及其有效的生态半衰期在鱼类之间可能有所不同，但是直到最近，放射性铯代谢中是否存在种间差异尚不明确。我们比较了在受控条件下五个鲑鱼物种中¹³⁷ Cs的营养转移。在固定的时间内给鱼喂食含有200 Bq kg ^-1湿重浓度为¹³⁷ Cs的饲料。虽然在固定时期内某个物种中单个鱼类的污染水平几乎没有差异，但在所检查的物种中¹³⁷ Cs的吸收率在统计学上是不同的，其有效半衰期为¹³⁷Cs范围为49-84天。校正生长差异后，在两个实验中，物种之间的¹³⁷ Cs数量下降速率没有明显差异。在Oncorhynchus mykiss和O. masou中，有效半衰期最短，这两个物种在两个实验中均表现出最佳的生长速率，表明稀释效应与生长有关。当在209–294天的时间内连续进料200 Bq kg ^-1湿重¹³⁷ Cs的浓度时，这五个物种的污染水平为216–240 Bq kg ^-1湿重，达到稳态值。我们的结果表明，尽管伴随着体重的变化，代谢率也没有影响鱼类中¹³⁷ Cs的污染水平，这意味着饮食中的污染水平强烈地决定了鱼类中的污染水平。