Potential Effects of Contaminants on Fraser River Sockeye Salmon

Nevertheless, it is possible that exposure to endocrine disrupting compounds are causingother types <strong>of</strong> effects that could be sufficient to adversely affect the survival, growth, orreproduction <strong>of</strong> sockeye salmon in the Fraser River Basin. There is a growing body <strong>of</strong>evidence from laboratory and field studies indicating that exposure to endocrine disruptingcompounds can compromise the immune system <strong>of</strong> exposed fish. O’Halloran et al. (1998)conducted a review <strong>of</strong> the literature and concluded that metals, TBT, organochlorine andorganophosphate pesticides, PAHs, PCBs, PBBs, and PCDDs/PCDFs elicit significantimunotoxicity in fish. Importantly, such adverse effects on immune response have beendemonstrated in Pacific salmon exposed to PAHs, PCBs, and mixtures <strong>of</strong> contaminants(Arkoosh et al. 1991; 1994; Milston et al. 2003; Misumi et al. 2005). Reducedimmunocompetance associated with exposure <strong>of</strong> fish to these and other substances tendsto exacerbate disease states by lowering resistance and allowing the invasion <strong>of</strong> infectiousagents (Zelik<strong>of</strong>f and Cohen 1996; Jacobson et al. 2003).Reduced immunocompetance represents a serious concern for outmigrating sockeyesalmon smolts. To evaluate the significance <strong>of</strong> exposure to endocrine disruptingcompounds on salmon smolts, Varanasi et al. (1993) collected chinook salmon fromcontaminated and uncontaminated estuaries in Washington State and held these fish for 40days in saltwater. The results <strong>of</strong> this study showed that chinook salmon with higherexposure to endocrine disrupting compound-type contaminants (as indicated by PAH,PCB, and organochlorine pesticide concentrations in stomach contents, PAH metabolitesin fish bile, and hepatic cytochrome P450 activity) had lower survival during the transitionto the saltwater environment than did fish in the low exposure treatment groups. Morespecifically, chinook from the Duwamish Waterway and Puyallup estuary (twocontaminated systems) had 56% and 58% survival, respectively, after 40 days in saltwater. By comparison, survival rates for fish from the relatively uncontaminated Nisquallyestuary (81%), from the Green River Hatchery (86%), and Kalama Creek Hatchery(88%) were significantly higher. In addition, impaired survival during the parr-smolttransformation has been reported for Atlantic salmon exposed to low levels <strong>of</strong> atrazine(i.e., >1 µg/L; Fairchild et al. 2002). Adverse effects on the parr-smolt transformationand impaired ability <strong>of</strong> fish to adapt to saline conditions have also been reported forAtlantic salmon exposed to 4-nonylphenol (at 5 µg/L) and estrogen (at 0.1 µg/L; Fairchildet al. 1999). Furthermore, juvenile chinook salmon that were exposed to PAHs or PCBshad higher mortality (i.e., about 60%) than control fish (i.e., about 15%) 14 days afterexposure to the marine pathogen, Listenella anguillarum (the bacterium formerly knownas Vibrio anguillarum; Arkoosh et al. 1998). Finally, Filby et al. (2007) demonstratedthat effects on the immune system were greater when fish were exposed to mixtures <strong>of</strong>endocrine disrupting compounds (i.e., compared to exposure to individual chemicals).104