Potential Effects of Contaminants on Fraser River Sockeye Salmon

Location <strong>of</strong> NatalStreamDuration <strong>of</strong>ExposureExposure IntensityUpper watershed 18 - 24 days High for 6 daysLow to Moderate for up to 18 daysMiddle watershed 12 - 18 days High for 6 daysLow for up to 12 daysLower watershed 6 - 12 days High for 6 daysLow for up to 6 daysPait and Nelson (2002) reviewed the literature describing the effects on fish associatedwith exposure to endocrine disrupting compounds in laboratory (Table 6.2) and fieldstudies (Table 6.3). The indicators considered in that evaluation <strong>of</strong> the effects <strong>of</strong>endocrine disrupting compounds on fish included vitellogenin levels, testosterone levels,17â-estradiol levels, gonadosomatic index scores, gonadal development, and incidence <strong>of</strong>intersex. The results <strong>of</strong> studies conducted with individual chemicals indicate that longtermexposure to a variety <strong>of</strong> endocrine disrupting compounds can have significant effectson such ecologically-relevant endpoints as the incidence <strong>of</strong> intersex in males and impairedgonadal development in fish. The results <strong>of</strong> field studies confirm that exposure tomunicipal wastewater treatment plant effluent or pulp and paper mill effluents canadversely affect reproduction <strong>of</strong> fish. Such reproductive abnormalities can lead topopulation level impacts on exposed fish species (Sparks et al. 2005).For Fraser River sockeye salmon, exposure to endocrine disrupting compounds duringincubation and rearing is likely to be negligible. Therefore, significant exposure toendocrine disrupting compounds is likely to occur primarily during migration periods. Theduration <strong>of</strong> exposure to endocrine disrupting compounds during smolt outmigration orupstream migration <strong>of</strong> adults is likely to be on the order <strong>of</strong> 6 to 24 days for sockeyesalmon. For this reason, data from laboratory or field studies, compiled by Pait andNelson (2002), with exposure durations <strong>of</strong> 30 days (i.e., consistent with the duration <strong>of</strong>exposure for the most highly exposed stocks during migration) were considered toevaluate potential effects on Fraser River sockeye salmon associated with exposure toendocrine disrupting compounds.The results <strong>of</strong> the laboratory studies conducted on multiple species <strong>of</strong> fish, includingsalmonids, demonstrated that induction <strong>of</strong> vitellogen production was commonly observedin fish exposed to endocrine disrupting compounds for < 30 days (Pait and Nelson 2002).In some laboratory studies, gonadosomatic indices were altered relative to control fish. In102