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MS
PowerPoint Presentation:
Elevated
levels of persistent
organic pollutants
in Puget Sound salmon:
the importance of
residency in Puget
Sound. |
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Orca study focuses
on contaminants in
Puget Sound salmon
Posted April 2005
Summary
The resident killer whale population in the Pacific
Northwest has declined rapidly over the past decade, prompting the National
Marine Fisheries Service in 2004 to propose the species as "threatened" under
the federal Endangered Species Act. Marine biologists believe chemical
contaminants and pesticides - absorbed by salmon and other fish that make
up a majority of the orcas' diet - may be a key factor in the resident
population's decline.
Contaminants in salmon were
the focus of a joint study recently completed by the Washington Department
of Fish and Wildlife and the NOAA Northwest Fisheries Science Center.
The study found significantly higher levels of certain contaminants in Puget Sound salmon - particularly chinook salmon - than in those collected in other areas of the Pacific coast.
In the mid-1990s, 98 resident killer whales ranged between Puget Sound and the Georgia Strait, feeding on salmon, rockfish, herring, squid and other fish. But by 2001, the number of "southern residents" in the J, K and L pods had declined to just 81 animals, while killer whale populations in Alaska continued to grow.
A status report on the southern residents issued by the Washington Department of Fish and Wildlife (WDFW) in 2004 suggests three likely factors in the orcas' decline:
- Disturbance by underwater noise and vessel traffic;
- A reduction in the abundance of salmon, a major food source for the southern residents; and
- Exposure to chemical contaminants, which are ingested by the killer whales through their prey and have been linked to reduced reproductive rates and autoimmune deficiencies in various marine mammals.
In 2000, a WDFW research team joined with fisheries scientists at the NOAA Northwest Fisheries Science Center to develop a better understanding of contaminant levels in Puget Sound salmon. Although several studies had examined contaminants in killer whales, little data existed to compare contaminants in salmon from Puget Sound salmon with other locations.
In the course of their study, the joint team analyzed samples from 180 whole salmon collected from Puget Sound and the Strait of Georgia, and compared the Puget Sound fishes' contaminant levels to those of 217 salmon collected from six other locations on the Pacific Coast.
One key finding was that summer/fall chinook salmon in Puget Sound contained levels of polychlorinated biphenyls (PCBs) three times higher than those tested in other areas of the Pacific coast. They also contained higher concentrations of polybrominated diphenyl ethers (PBDEs).
PCBs, once used to insulate electrical equipment but banned in the 1970s, are considered carcinogenic in humans. PBDEs, used as flame-retardants in electronics, building materials and textiles, are believed by human health officials to cause neurological damage in infants. Both chemical compounds persist in the environment, tending to accumulate in animals high on the food chain.
Although the contaminant study was not designed to measure risks to humans, the study team shared its data with the Washington Department of Health, the state agency responsible for establishing human consumption guidelines for fish and other food. No state guidelines have been issued for the consumption of salmon.
In collecting salmon for the study, the research team selected seven sites - from the Sacramento River to the Skeena River in British Columbia - covering the full summer feeding range of the southern and northern resident killer whale populations. For comparative purposes, the 50 chinook salmon sampled in Puget Sound were collected at two different times of the year: late summer, when migratory salmon are present and November, when resident salmon predominate.
In addition to those findings already cited about Puget Sound chinook salmon, the study team documented several other trends in salmon-borne contaminants. Their findings, illustrated in the accompanying slide presentation, are summarized below:
- Contaminant levels in all five species of Pacific salmon (chinook, coho, sockeye, chum, pink) were higher in Puget Sound than in those sampled from the north coast of British Columbia near the Skeena and Kimsquit rivers.
- The highest levels of all types of contaminants were found in chinook salmon, which generally feed higher in the food web than other types of salmon.
- PCB concentrations were highest in chinook salmon collected in November, assumed o be year-round residents of Puget Sound.
- Puget Sound chinook salmon contained lower levels of DDT, a pesticide banned in the United States, than those returning to the Columbia and the Sacramento Rivers.
- Tests conducted for hexachlorobenzene (HCB), a pesticide and industrial byproduct, showed slightly elevated concentrations in chinook salmon collected in British Columbia compared to those from Puget Sound and other locations sampled.
These findings are consistent with an analysis of 210 Puget Sound chinook fillet samples collected by WDFW from 1992-96 during a study for the Puget Sound Ambient Monitoring Program. WDFW plans to further investigate the degree to which residency in Puget Sound increases contaminant exposure for Puget Sound chinook salmon. The department also plans to evaluate the role of hatchery rearing practices that encourage residency in Puget Sound.
The contaminant study was designed by Sandie O'Neill, a WDFW research scientist with a bachelor of science degree in marine biology from the University of Newfoundland and a master of science degree in fish ecology from the University of British Columbia. James West, another WDFW research scientist, also contributed to the study. West holds a bachelor of science degree in marine biology from South Hampton College and a master of science degree in zoology from the University of Hawaii.
Margaret Krahn, Ph.D., supervisory research chemist at the Northwest Fisheries Science Center, oversaw the chemical analysis of samples used in the study. Other research chemists from the science center who participated in the study were Gina Ylitalo, Jennie Bolton and Donald Brown, Ph.D.
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