Monster Seminar Jam - Persistent Organic Pollutants
Gina Ylitalo, Northwest Fisheries Science Center, NOAA Fisheries
The population of southern resident killer whales (Orcinus orca) that live in the waters of Puget Sound during May through October was nearly 100 individuals in the mid-1990's but declined to 84 animals in 2004. Due to this population decline, NOAA Fisheries has recently proposed to list southern resident population as threatened under the Endangered Species Act. Potential factors that may be contributing to the decline of southern resident killer whales include: exposure to high levels of toxic persistent organic pollutants (POPs), reduced prey quality or quantity and noise and disturbance from vessel traffic.
Studies to date indicate that southern resident killer whales contain higher concentrations of POPs than levels measured in other resident killer whale populations that occur in the North Pacific. Elevated contaminant exposure in southern residents may be attributed to dietary differences compared to other North Pacific residents or to regional differences in concentrations of POPs in their prey. Based on observational data and stomach contents analyses, one study reported that during the summer months, the primary prey of northern and southern resident killer whales are salmon, especially Chinook salmon. To determine if Pacific salmon population present in the summer feeding areas of southern resident whales are more contaminated than other populations of free-ranging Pacific salmon that occur in the summer feeding range of northern resident whales, whole body samples of five species of Pacific salmon from urbanized and non-urbanized locations were analyzed for POPs to assess species-specific body burdens of these compounds. Within Puget Sound, we also analyzed resident stocks of Chinook salmon to determine if residency in Puget Sound increased contaminant concentrations. Our results indicate that contaminant concentrations were higher for Chinook salmon compared to other Pacific salmon species, likely due to their higher trophic position compared to other species of salmon. In addition, Puget Sound stocks of Chinook and coho had significantly higher concentrations of POPs than the other Pacific coast populations. We also found that levels of POPs were highest in Chinook salmon known to be resident in Puget Sound, than all other ocean-reared populations.. Furthermore, contaminant concentrations increased with size (and age), suggesting increased the residency of salmon in Puget Sound increases exposure to POPs. These data suggest that Chinook salmon, especially Puget Sound populations, are a likely source of POPs to southern resident killer whales We also examined ratios of contaminants in southern residents and their prey to elucidate potential sources or pathways of exposure to POPs in these predators and found that southern resident killer whales are more likely feeding on salmon than other prey fish species from the Puget Sound region.
To assess whether changes in prey quality may be contributing to the decline of southern residents, caloric content and proximate composition (e.g., total protein, lipid content) of these salmonids are planned. The percent lipid analyses are completed and our results show that Chinook and sockeye salmon contain higher lipid content than the other species of Pacific salmon. In the future, we will combine proximate analyses and caloric content with estimates of prey availability and average size to determine the differences in prey quality and quantity among the various known and potential prey items of southern residents.
Date and Time:
February 3, 2005,
11:00 am - 12:30 pm