Management of Snake River fall Chinook has been hindered by a great deal of uncertainty regarding key aspects of the ESU.  In particular, differential detectability of redds across source populations has limited the ability to accurately develop run reconstructions.  Further, migratory patterns of yearling migrants are largely unknown but spatially variable (Hegg et al. 2013), which makes it difficult to manage this segment of the population.  Therefore, we propose to conduct micro-chemical and micro-structural studies of otoliths in an effort to reduce these uncertainties.  In addition, information derived from these studies will be incorporated into ongoing efforts to develop life-history models and models of the fitness of alternative life-history strategies.