[en] The long-distance migrations of commercial fish in the arctic seas may lead to the biological transfer of artificial radionuclides from highly contaminated local zones in the arctic seas to remote non-contaminated areas. Based on experimental data the dynamics of ¹³⁷Cs bioaccumulation in fish from the Barents Sea (arcto-norwegian cod) was analysed. It was demonstrated that the ¹³⁷Cs concentration factors for arctic fish were not constant, but gradually changed from 28 ± 5 in 1979 up to 182 ± 48 in 1992 with a slow decrease in subsequent years. The conclusion reached was that the radionuclide 'concentration factor' approach to the prediction of arctic fish contamination was not very applicable. An original calculation method is proposed for modelling the dynamics of radioactive contamination of fish, with consideration of fish feeding behaviour, growth and seasonal migrations. Results of the computer simulation of the fish contamination in the Barents Sea after a hypothetical accidental release of 1 TBq of ¹³⁷Cs from the radioactive waste dumping site are presented. (author)