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Potential Effects of Contaminants on Fraser River Sockeye Salmon

Potential Effects of Contaminants on Fraser River Sockeye Salmon

Potential Effects of Contaminants on Fraser River Sockeye Salmon

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have been observed in recent years. Furthermore, feminizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>on</strong>e male sockeyesalm<strong>on</strong> (i.e., a genetic male with ovaries) collected in 2007 was reported (Siska Traditi<strong>on</strong>sSociety 2009). Such changes in salm<strong>on</strong> physiology are not unlike those that could occurin resp<strong>on</strong>se to endocrine disrupting compounds and/or other c<strong>on</strong>taminants.Overall, the results <str<strong>on</strong>g>of</str<strong>on</strong>g> this evaluati<strong>on</strong> also dem<strong>on</strong>strate that the c<strong>on</strong>taminant exposurescannot be discounted as a potential c<strong>on</strong>tributing factor for resp<strong>on</strong>ses <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>Fraser</strong> <strong>River</strong>sockeye salm<strong>on</strong> over the past two decades and/or for the low returns <str<strong>on</strong>g>of</str<strong>on</strong>g> sockeye salm<strong>on</strong> tothe river in 2009. For all five lines-<str<strong>on</strong>g>of</str<strong>on</strong>g>-evidence, it was not possible to categoricallydisprove the hypothesis that exposure to endocrine disrupting compounds or otherc<strong>on</strong>taminants <str<strong>on</strong>g>of</str<strong>on</strong>g> emerging c<strong>on</strong>cern have c<strong>on</strong>tributed to the decline <str<strong>on</strong>g>of</str<strong>on</strong>g> <strong>Fraser</strong> <strong>River</strong> sockeyesalm<strong>on</strong>. Therefore, it is c<strong>on</strong>cluded that exposure to endocrine disrupting compoundsand/or other c<strong>on</strong>taminants <str<strong>on</strong>g>of</str<strong>on</strong>g> emerging c<strong>on</strong>cern represents a possible c<strong>on</strong>tributing factor inthe decline <str<strong>on</strong>g>of</str<strong>on</strong>g> sockeye salm<strong>on</strong> abundance in the <strong>Fraser</strong> <strong>River</strong> basin. The pathways throughwhich such effects <strong>on</strong> sockeye salm<strong>on</strong> abundance could be expressed include:• Immunosuppressi<strong>on</strong> due to exposure to endocrine disrupting compounds (suchas PAHs, PCBs, PBDEs, and other endocrine disrupting compounds) duringsmolt outmigrati<strong>on</strong> and associated increased susceptibility to infecti<strong>on</strong> bydisease agents, leading to higher rates <str<strong>on</strong>g>of</str<strong>on</strong>g> mortality;• Reduced ability to adapt to c<strong>on</strong>diti<strong>on</strong>s in marine ecosystems due to exposure toendocrine disrupting compounds (such as APEOs and associated metabolites)during smolt outmigrati<strong>on</strong>, an effect that is likely enhanced by increasedsusceptibility to infecti<strong>on</strong> by disease agents; and,• Reduced survival <str<strong>on</strong>g>of</str<strong>on</strong>g> sockeye salm<strong>on</strong> eggs due to magnificati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> persistent,bioaccumulative, and toxic c<strong>on</strong>taminants (such as PCBs, PCDDs, and PCDFs)in g<strong>on</strong>ad tissues during upstream migrati<strong>on</strong>. This effect is likely to be mostsevere for those stocks that travel the l<strong>on</strong>gest distances during upstreammigrati<strong>on</strong>.In additi<strong>on</strong>, it is possible that exposure <str<strong>on</strong>g>of</str<strong>on</strong>g> adult sockeye salm<strong>on</strong> to endocrine disruptingcompounds and/or other c<strong>on</strong>taminants <str<strong>on</strong>g>of</str<strong>on</strong>g> emerging c<strong>on</strong>cern in the lower <strong>Fraser</strong> <strong>River</strong>during upstream migrati<strong>on</strong> could result in some level <str<strong>on</strong>g>of</str<strong>on</strong>g> immunosuppressi<strong>on</strong>. Such effectscould lead to increases in en-route and/or pre-spawning mortality, especially for thosestocks that migrate upstream at times when water temperatures exceed 18 C (Hinch andoMartins 2011). Such sockeye salm<strong>on</strong> adults would be particularly susceptible to infecti<strong>on</strong>by the pathogen, Parvicapsula sp. Resolving uncertainties regarding the nature,119

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