Potential Effects of Contaminants on Fraser River Sockeye Salmon

• Estimating realistic exposure point concentrations;• Identifying salmonid-specific toxicity thresholds; and,• Calculating effect-based hazard quotients.Three types <strong>of</strong> data were used to evaluate risks to sockeye salmon associated withexposure to the contaminants <strong>of</strong> concern, including surface-water chemistry, sedimentchemistry, and fish-tissue chemistry data. The results <strong>of</strong> this assessment indicate thatexposure to contaminated surface water and sediment or accumulation <strong>of</strong> contaminants infish tissues pose potential hazards to sockeye salmon utilizing spawning, rearing, ormigration habitats within the Fraser River Basin. More specifically, these results indicatenumerous contaminants <strong>of</strong> concern occur in one or more habitats at concentrationssufficient to adversely affect the survival, growth, or reproduction <strong>of</strong> Fraser River sockeyesalmon. These substances include TSS, six metals (aluminum, chromium, copper, iron,mercury and silver), and phenols (Table 5.18). However, the results <strong>of</strong> supplementalanalysis <strong>of</strong> the available data indicate that water quality conditions in freshwater habitats,as indicated by the concentrations <strong>of</strong> the contaminants <strong>of</strong> concern included in the waterquality index, are likely not the primary factor influencing sockeye salmon productivity inthe study area. These supplemental results showed that water quality (as indicated bywater quality index scores) does not exhibit strong temporal trends, as would be expectedif the declines in sockeye salmon abundance over the past 20 years were primarily causedby water quality impairments. In addition, the productivity <strong>of</strong> sockeye salmon (asindicated by life-cycle Ricker residuals) was not correlated with water quality index scoresin a way that would suggest that water quality conditions are playing a significant role indictating sockeye salmon abundance. However, the observed results <strong>of</strong> the analysis andthe limitations on the available data make it difficult to conclude that water quality is not afactor that has contributed to the declines <strong>of</strong> sockeye salmon in the study area since about1990. Decreases in the productivity <strong>of</strong> sockeye salmon stocks that utilize freshwaterhabitats for extended period <strong>of</strong> time implicates freshwater conditions as a factorcontributing to the declines <strong>of</strong> this species in the Fraser River Basin. Further evaluation isneeded to elucidate the roles <strong>of</strong> suspended sediments in spawning habitats, sedimentdeposition in incubation habitats, and nutrients in rearing habitats on sockeye salmonproductivity and abundance.Exposure to contaminated sediments also has the potential to adversely affect sockeyesalmon in the Fraser River basin. Although the available data were limited, the results <strong>of</strong>the risk assessment showed that iron and/or nickel occurred in sediments at concentrationssufficient to adversely affect exposed sockeye salmon in the Lower Fraser River Area <strong>of</strong>71