Fig. 2. Confounding changes in factors affecting Snake River salmon over the last four decades: number of dams passed by Snake River salmon (Schaller et al. 1999); total hatchery releases in Snake River Basin (Williams et al. 1998); historical fraction of spring/summer chinook transported in barges, as estimated by two different passage models, CRiSP and FLUSH (Marmorek et al. 1998b); and Pacific Decadal Oscillation (higher values associated with poorer ocean conditions for Snake River salmon; Mantua et al. 1997).