Potential Effects of Contaminants on Fraser River Sockeye Salmon

Chilko River, Quesnel River, Nechako River, and Bowron River areas <strong>of</strong>interest, and the reference area (i.e., Fraser River at Red Pass).• Data on the concentrations <strong>of</strong> chemicals <strong>of</strong> potential concern in surface wateror sediments were not available for the majority <strong>of</strong> the stream reaches that areused for spawning and incubation by sockeye salmon in the study area (e.g.,Upper Pitt River, Chilliwack River, Stuart Lake, tributaries to theTakla/Trembleur Lake system, Upper Adams River). Accordingly, exposure tochemicals <strong>of</strong> potential concern during spawning and incubation were estimatedusing data available for other locations (typically downstream orhydrologically-connected sites) in each area <strong>of</strong> interest. This extrapolation <strong>of</strong>the available data to upstream sites substantially increased uncertainty in theresults <strong>of</strong> the exposure assessment for the spawning and incubation period.• Data on the concentrations <strong>of</strong> chemicals <strong>of</strong> potential concern in surface wateror sediments were not available for most <strong>of</strong> the nursery lakes or stream reachesthat are used for freshwater rearing by sockeye salmon in the study area (e.g.,Chilliwack Lake, Kakawa Lake, the Stuart/Takla/Trembleur Lake System,Adams Lake, Lilliooet Lake). Accordingly, exposure to chemicals <strong>of</strong> potentialconcern during freshwater rearing was generally estimated using data availablefor other locations (typically downstream or hydrologically-connected sites) ineach AoI. This extrapolation <strong>of</strong> the available data to unsampled lacustrine sitessubstantially increased uncertainty in the results <strong>of</strong> the exposure assessment forthe freshwater rearing period.• Fish-tissue chemistry data were located for a limited number <strong>of</strong> sockeye salmonstocks (i.e., Early Stuart, Weaver, and Adams stocks) and a limited number <strong>of</strong>contaminants. No data were located on the levels <strong>of</strong> persistentbioaccumulative contaminants in the tissues <strong>of</strong> outmigrating smolts from theFraser River. This limitation makes it difficult to evaluate exposure <strong>of</strong> sockeyesalmon to persistent bioaccumulative contaminants. As a result, risks tosockeye salmon utilizing spawning and rearing habitats within numerous areas<strong>of</strong> interest could not be evaluated for bioaccumulative contaminants.• Data were primarily collected for the purposes <strong>of</strong> environmental impactassessments, water quality objectives monitoring, trend analysis, compliancemonitoring, and background characterization. As such, water quality samplingstations were only infrequently co-located with sockeye-use areas. As impactsto freshwater habitats can be localized, the available data may not accuratelyreflect the exposure scenarios for Fraser River sockeye salmon.126