Potential Effects of Contaminants on Fraser River Sockeye Salmon

Toxicity Thresholds for Sediment - A total <strong>of</strong> five substances were identified ascontaminants <strong>of</strong> concern in sediment based on the results <strong>of</strong> the preliminary evaluationand subsequent refinement process (see Section 5.1). Sockeye salmon-specific,salmonid-specific, or fish-specific sediment quality guidelines were not located in theliterature to support the detailed evaluation <strong>of</strong> sediment chemistry data for the FraserRiver Basin. For this reason, effects-based sediment quality guidelines for theprotection <strong>of</strong> benthic invertebrates were obtained from multiple jurisdictions andreviewed to identify toxicity thresholds that could be used to assess sediment qualityconditions in the study area. A tiered-approach was used to select toxicity thresholdsfor use in the evaluation and involved:• Selecting probable effect concentrations (PECs) or median effectconcentrations (MECs) from MacDonald et al. (2000a; 2000b) when suchvalues were available;• Selecting probable effect levels (PELs) from CCME (1999) or MacDonald(1994) when PECs/MECs were not available; and,• Selecting the lowest effect levels from Nagpal et al. (2006) for thosesubstances for which none <strong>of</strong> the other sediment quality guidelines wereavailable.Such toxicity thresholds represent the concentrations <strong>of</strong> contaminants <strong>of</strong> concernabove which adverse effects on the benthic invertebrate community are likely to beobserved when the contaminants <strong>of</strong> concern occur in complex mixtures with othercontaminants. The toxicity thresholds that were selected for evaluating sedimentchemistry data from the Fraser River Basin are presented in Table 5.2.Toxicity Thresholds for Fish Tissues - Accumulation <strong>of</strong> certain contaminants intissues has the potential to adversely affect the survival, growth, or reproduction <strong>of</strong>sockeye salmon. In this study, toxicity thresholds for fish tissues were identified fromselected reviews <strong>of</strong> the scientific literature that evaluate adverse effects on fishassociated with accumulation <strong>of</strong> contaminants <strong>of</strong> concern in their tissues. The toxicitythresholds that were selected for evaluating fish-tissue chemistry data from the FraserRiver Basin are as follows:• Mercury - 0.4 µg/g WW (Dillon et al. 2010);• Selenium - 1.58 µg/g WW (USEPA 2010b); and,61