Tritium dynamics in juvenile rainbow trout, Salmo gairdneri

Juvenile rainbow trout, Salmo gairdneri, were maintained in tritiated water, fed a tritiated diet or both, and the specific activity of 3H in the fish was determined during and following 3H exposure. Tissue water 3H-equilibrated rapidly with the ambient water (estimated half-life less than 30 min) and maintained a steady-state specific activity similar to ambient. In contrast, the steady-state specific activity of organically bound 3H was significantly affected by that of the diet. The steady-state specific activity of organically bound 3H of trout maintained in tritiated water but fed non-tritiated diets was approximately 20% of that of the ambient water. This steady-state specific activity was achieved relatively quickly (half-life approximately 1 d) and presumably reflects the exchangeable H of the fish. For trout fed a tritiated diet, in either tritiated or non-tritiated water, steady-state specific activities of organically bound 3H were on the order of 80% of that of the diet. These steady-state specific activities were reached much more slowly (estimated half-lives of 18-32 d) and are likely to represent the accumulation of non-exchangeable 3H in the organic material of the trout.