Potential Effects of Contaminants on Fraser River Sockeye Salmon

(See Chapters 4 and 5 for further information). However, actual exposure to theendocrine disrupting compounds contained in wastewater treatment plant effluents canoccur only when these key life stages are present in exposure areas during periods <strong>of</strong>discharge to receiving water streams. As such, it is necessary to determine whensockeye salmon are present in areas that receive discharges from municipal wastewatertreatment plants.For incubating sockeye salmon eggs and alevins, exposure to wastewater treatmentplant effluent is likely to be negligible for most conservation units. However,significant exposure to endocrine disrupting compounds associated with municipalwastewater is likely to occur for the Harrison River sockeye salmon spawningdownstream <strong>of</strong> the wastewater treatment plant located at Harrison Hotsprings. Inaddition, certain stocks <strong>of</strong> sockeye salmon (e.g., Salmon River) associated with theShuswap River conservation unit may be exposed to diluted wastewater treatmentplant effluent during incubation.No information was located that indicated that any <strong>of</strong> the wastewater treatment plantsin the Fraser River Basin discharge directly into nursery lakes used for early rearing bysockeye salmon. Accordingly, it is assumed that exposure <strong>of</strong> sockeye salmon towastewater treatment plant effluent is negligible for virtually all stocks in the studyarea. The exception could be the Harrison River stocks that rear in backwater areasand sloughs within the Lower Fraser River for a period <strong>of</strong> time before migrating toGeorgia Strait.There are numerous wastewater treatment plant located along the migration corridorsfor sockeye salmon in the Fraser River Basin (Figure 3.12). The magnitude andduration <strong>of</strong> exposure to endocrine disrupting compounds associated with wastewatertreatment plant effluents is a function <strong>of</strong> the level <strong>of</strong> treatment used (i.e., primary,secondary, or tertiary treatment), the volume <strong>of</strong> effluent discharged to receivingwaters, the dilution capacity <strong>of</strong> receiving water systems, distance travelled duringdownstream or upstream migration, and sockeye salmon residence time in areas withsignificant effluent discharges. As residence time <strong>of</strong> outmigrating smolts and upstreammigrating adults in various sections <strong>of</strong> the Fraser River mainstem is unknown for moststocks, it is assumed that the magnitude and duration <strong>of</strong> exposure to endocrinedisrupting compounds in wastewater treatment plant effluents are high for up-riverstocks with the longest migration distances (i.e., those returning to the Quesnel,Bowron, and Nechako river watersheds), moderate for stocks with intermediatemigration distances (i.e., those returning to the Chilko, Seton-Portage, and Thompson96