Jun 1, 2016

Site-specific objectives (SSO) for copper, developed in 2007, called for further study on the potential toxicity of copper to the olfactory system of salmonids.  The RMP, in partnership with the Copper Development Association, funded studies by researchers at the National Marine Fisheries Service to address this data gap.  A journal article summarizing this work was published in June.  The studies indicated a threshold for copper olfactory toxicity in freshwater-phase juvenile salmon of around 5 μg/L in freshwater.  As juveniles migrate into estuaries and encounter increased salinities of 10 parts per thousand (ppt), this threshold increases to >50 μg/L.  After juvenile salmon transition to smolts within the Estuary, the threshold remains >50 μg/L in either estuarine water of 10 ppt or seawater.  The current SSOs for copper (6.0 – 6.9 μg/L chronic and 9.4 – 10.8 ug/L acute in different segments of the Bay), therefore, appear to protect the olfactory system of juvenile salmon from toxicity under Bay conditions.