Potential Effects of Contaminants on Fraser River Sockeye Salmon

8.5 Evaluation <strong>of</strong> the <strong>Potential</strong> <strong>Effects</strong> <strong>of</strong> <strong>Contaminants</strong> <strong>of</strong> Concern on FraserRiver Sockeye SalmonA risk-based approach was used to evaluate the potential effects on sockeye salmonassociated with exposure to contaminants <strong>of</strong> concern in the Fraser River Basin. Thisapproach involved:• Refining the list <strong>of</strong> contaminants <strong>of</strong> concern;• Estimating more 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 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.Comparison <strong>of</strong> surface-water chemistry data to the selected toxicity threshold indicate thatexposure to surface water can adversely affect the survival, growth, or reproduction <strong>of</strong>Fraser River sockeye salmon. More specifically, concentrations <strong>of</strong> TSS, six metals(aluminum, chromium, copper, iron, mercury and silver), and phenols are sufficient toadversely affect sockeye salmon. However, the results <strong>of</strong> supplemental analysis <strong>of</strong> thesedata indicate that water quality conditions in freshwater habitats may not be the primaryfactor influencing sockeye salmon productivity in the study area. These supplementalresults showed that water quality (as indicated by water quality index scores) does notexhibit strong temporal trends, as would be expected if the declines in sockeye salmonabundance over the past 20 years were primarily caused by water quality impairments. Inaddition, the productivity <strong>of</strong> sockeye salmon (as indicated by life-cycle Ricker residuals)was not correlated with water quality index scores in a way that would suggest that waterquality conditions (as indicated by levels <strong>of</strong> conventional variables, major ions, nutrients,metals, or phenols) are playing a significant role in dictating sockeye salmon abundance.However, the results <strong>of</strong> the analysis and the limitations on the available data make itdifficult to conclude that water quality is not a factor that has contributed to the declines<strong>of</strong> sockeye salmon in the study area since about 1990. Further evaluation is needed toelucidate the roles <strong>of</strong> suspended sediments in spawning habitats, sediment deposition in136