Spatial extent, magnitude, and patterns of persistent organochlorine pollutants in Pacific herring (Clupea pallasi) populations in the Puget Sound (USA) and Strait of Georgia (Canada)

We examined the geographic distribution and magnitude of three persistent organic pollutants (POPs) in Pacific herring, representing three populations from Puget Sound, Washington State, USA and three from the Strait of Georgia (British Columbia, Canada and Washington State). We measured PCBs, DDTs and DDT isomers, and hexachlorobenzene in whole herring using high performance liquid chromatography, which provided a relatively inexpensive estimation of total PCBs, including the most commonly encountered congeners, and DDT isomers. Puget Sound herring were 3 to 9 times more contaminated with polychlorinated biphenyls (PCBs) compared to Strait of Georgia herring and 1.5 to 2.5 times more contaminated with DDTs. Hexachlorobenzene levels were low in all samples, relative to PCBs and DDTs, and one Strait of Georgia population (Cherry Point) had significantly lower HCB levels than the rest. A multidimensional scaling map of the pattern or “fingerprint” of POPs in the six herring populations suggests strong environmental segregation of Puget Sound herring from the Strait of Georgia populations, and isolation of all Strait of Georgia populations from each other. This segregation likely resulted from differential exposure to contaminants, related to where these populations reside and feed, rather than differences in their age, size, trophic level, or lipid content.