Roles of food and sea water in the accumulation of radionuclides by marine fish

As a part of study on accumulation of radionuclides by marine fish, yellowtail, were marked by multiple radioisotopes (144Ce-144Pr, 016Ru-106Rh, 85Sr, 137Cs, 54Mn, 65Zn and 60Co) under certain conditions through food and water. The radioactivity of each tracer in the tissues or organs was determined by a Ge(Li) spectrometer in order to gain more knowledge concerning roles of food and water in the accumulation of radionuclides. Somewhat different distribution patterns of radionuclides were found in the whole bodies of the fish at the maximum accumulation with the difference in pathways. The results obtained in the excretion experiment for two weeks suggested that the turnover rate was different, depending on pathways through which the fish accumulated radionuclides. And the principal pathway in the accumulation of radionuclides by marine fish in natural sea was estimated. The results showed that (1) food rather than water supplied most of the 65Zn and 54Mn accumulated by fish, (2) 85Sr and 106Ru-106Rh were mainly accumulated via water and (3) the two pathways played almost the same role in the accumulation of 137Cs, 60Co and 144Ce-144Pr. Therefore, it is necessary to take into account these results for estimation of the extent of radioactive contamination in fish under natural marine ecosystem. (author)