Variation of 137Cs levels between sexes, body sizes and collection localities of mosquitofish, Gambusia holbrooki (Girard 1859), inhabiting a reactor cooling reservoir

Whole body concentrations of 137Cs were determined for 190 mosquitofish (Gambusia holbrooki) collected in April 1987 from three locations in a former cooling reservoir which had been contaminated with 137Cs from production reactor effluents between 1961 and 1964. Male fish collected near the point where the reactor effluent had entered the reservoir tended to have higher 137Cs concentrations than those from the other locations. Females did not differ in 137Cs concentrations between the three locations. Females at the site of contaminant entry tended to decrease in 137Cs concentration as body size increased. These results suggest that that radionuclide whole body concentrations may vary in unexpected ways between sex or size classes within a given species and that such differences may also vary within microgeographic scales. (author)