Non-radioactive rare earth elements (REE) were evaluated as potential markers in scales of hatchery-reared juvenile striped bass Marone saxatilis over a 12week feeding study. Uptake and retention levels of europium (Eu) and terbium (Tb) detected by neutron activation analyses at below 1 p,g/g could be related directly to dietary concentrations of the 2 elements and duration of feeding. Decreased relative concentrations following post-feeding could be related to scale mass increases and the inherent problem with detection techniques which analyze for amounts per unit mass. We compared our 1981 study with more recent similar studies as well as studies using different applications and detection techniques for REE. Low levels of REE uptake, limited availability and high cost of detection technology, masking effects resulting during post-release growth, and potential wild-sources of REE place tagging techniques by feeding REE beyond practicability for most field fisheries studies at the present time.
