To optimize conservation and restoration strategies for fish stocks it is important to identify the rearing habitats that produce the most successful individuals. However, tracking millions of migratory fish through multiple life stages seems to be impossible using conventional techniques. Using differences in the ratio of stable isotopes of strontium (Sr), found naturally in stream water, we have been able to distinguish juvenile Atlantic salmon (Salmo salar) from eight of ten rearing sites studied in Vermont streams. This demonstrates the potential for using environmental signals to determine the rearing stream from which salmon originate, and should help to guide restoration activities.

Kennedy, B., C.L. Folt, J. Blum and C. Page Chamberlain, Nature 387:766-767, 1997