Historical signatures of salmon in tree rings
using stable nitrogen isotopes
T. E. Reimchen, D. Mathewson and D.S. Harris (submitted)
Nutrients from salmon carcasses are incorporated into a diverse assemblage of aquatic and terrestrial species in coastal watersheds of western North America. Here we demonstrate that small samples of wood (30 mg) extracted from cores of riparian old growth trees contain detectable levels of salmon-derived nutrients (characterized by elevated 15N levels) and these nutrients can contribute up to 75% of the total nitrogen in the wood of trees from watersheds where salmon are abundant. Furthermore, comparisons among watersheds show that 15N levels are directly proportional to the numbers of salmon entering the streams although levels are correlated to tree size. This finding offers a novel tool for assessing the occurrence and potentially the relative abundance of salmon and other anadromous fish in past centuries from watersheds of North America, Europe and Asia and has applications for any regions with marine-terrestrial nitrogen transfer.