LESIG Home
Salmon Migration Studies
Over the past century, human-caused changes in San Francisco Bay ’s watershed have resulted in major declines in migratory fish populations, such as salmon. This decline may be caused by water development (upstream storage-dams and reservoirs), water diversion, and delta pumps, which cause mortality of young fry. To offset the declines of salmon populations, it is critical to distinguish between the various races of salmon that populate the different rivers. Graduate student Peter Weber and I are developing methods for distinguishing juvenile salmon stocks in this major watershed. Our methods involve examining the concentrations of trace elements and isotopic compositions along sequential growth layers of salmon otoliths (aragonitic ear stones) and scales. We have shown, for example, that the strontium isotopic compositions of otoliths from juvenile and adult salmon from the San Sacramento rivers are distinct. Further differentiation between tributary rivers may be possible using oxygen and carbon isotopes. For example, oxygen isotopic values increase from north to south in the Sacramento River watershed. Salmon reared in these rivers should therefore carry a chemical “fingerprint” of the watershed from which they originated.
PUBLICATIONS:
Peter K. Weber, Charles R. Bacon, Ian D. Hutcheon, B. Lynn Ingram, and Joseph L. Wooden (2005). Ion microprobe measurement of strontium isotopes in calcium carbonate with application to salmon otoliths. Geochimica et Cosmochimica Acta 69: 1225-1239.
Weber, P.K., Hutcheon, I.D., McKeegan, K.D., and Ingram, B.L. (2002) Otolith sulfur isotope method to reconstruct salmon (Oncorhynchus tshawytscha) life history. Can J. Fish. Aquat. Sci. V. 59, p. 587-591.
Ingram, B. L., and Weber, P.K. (1999) Salmon origin in California as determined by otolith strontium isotope compositions, Geology V. 27, p. 851-854.
Ingram, B.L, and Weber, P.K. (1998) Determining Salmon Stock Origin Using Strontium Isotopes, Interagency Ecological Program Newsletter, Summer.
Weber, P.K., Hutcheon, I.D., McKeegan, K.D., and Ingram, B.L. (2002) Otolith sulfur isotope method to reconstruct salmon (Oncorhynchus tshawytscha) life history. Interagency Ecological Program for the San Francisco Estuary Newsletter, V. 15, p. 16-21.
SF Bay 