Labeling Fish with an Activable Element

Abstract

An activable element was administrated for labeling fish, Oryzias latipes, by injecting samarium, one of the rare earth elements, into the abdominal cavity. The fish were killed at intervals varying from 1 to 600 d after the injection and exposed to a beam of thermal neutrons in a nuclear reactor. It was possible to distinguish the difference between labeled and unlabeled fish by the detection of 153Sm produced by (n, γ) reaction. The level of samarium detected remained almost constant even about 2 yr after the last injection. The second experiment using larger fish, Carassius auratus, revealed that samarium was retained in the internal organs.Key words: fish marking, activable tracer, activation analysis, samarium, Oryzias latipes, Carassius auratus