Adult fish delay at John Day Dam

Migrating adult salmonids have been found to delay for an inordinate time before passing John Day Dam. The fishways and flows there are not substantially different from those at other large dams, in particular those at the downstream Bonneville and The Dalles Dams, where apparently there are no such passage delays. Recent cooperative studies between the National Marine Fisheries Service (NMFS) and the U.S. Army Corps of Engineers (CofE) have suggested that these migratory delays are related to and may be caused by industrial pollutants in the forebay of John Day Dam (Damkaer 1983). In FY83, we have continued to observe the distributions and concentrations of some inorganic pollutants, especially fluoride, and have begun bioassay experiments to determine the effects on salmonids of low fluoride levels.