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Marine Toxic Contaminants

Species Monitored: Pacific Herring

Pacific herring (Clupea pallasi)

Pacific herring are important prey to many species of Puget Sound fish, seabirds and marine mammals; consequently, their health is a good general indicator of the health of the Puget Sound ecosystem. As adults, herring are pelagic and wide-ranging, but with the onset of spawning, they move into the shallow near-shore habitat where they deposit their eggs on marine vegetation and other substrates. During an incubation period of about 14 days, the fertilized eggs could be exposed to contaminants through either direct contact with the sediments or by the water washing over them. After hatching, the pelagic larvae gradually move from the near-shore habitat to the open water column where they mature and spend the majority of their life.

Being planktivorous, larval and adult herring may be exposed to pollutants that are present in the water column and plankton. And because the muscle tissues of the adults are relatively high in lipids, they may readily accumulate lipophilic contaminants such as PCBs. In females, a portion of these lipophilic contaminants may be passed to the young along with the lipids used for egg development.

Historic studies by Fish and Wildlife have identified a number of discrete spawning stocks within South, Central and North Puget Sound. Examination of average contaminant exposure in the adult spawning stocks should reflect environmental contamination from the geographic areas in which these fish reside. Furthermore, because they are a short-lived species 1, their contaminant loads reflect recent environmental conditions in their habitats.

The Fish Component completed a pilot study on contaminants in herring in 1995 and began annual baseline monitoring in 1999. Click for sampling locations.

  1. Age of the oldest herring collected by the Fish Component were estimated at 6 years.