Potential Effects of Contaminants on Fraser River Sockeye Salmon

Spitsbergen et al. (1991) reported that the survival <strong>of</strong> lake trout eggs, alevins, and frywas significantly reduced when eggs were exposed to T4CDD contaminated water fora period <strong>of</strong> 48 hours. Long-term survival was slightly but significantly impaired (i.e.,-1reduced by 2%) at a tissue residue level <strong>of</strong> 0.04 ìgkg egg, while 100% mortality-1occurred at 0.40 ìgkg egg. In a separate study, Walker et al. (1991) reported thatthe lethal concentration (LC 50) <strong>of</strong> T4CDD in lake trout eggs, considering survival to 60-1days after swim-up, was 0.065 ìgkg egg. More recently, DeBruyn et al. (2004)reported that decreased survival <strong>of</strong> salmon eggs (30% reduction) is observed at2,3,7,8-TCDD-toxic equivalent level <strong>of</strong> 3 ng/kg lipid in roe. This toxicity threshold islikely relevant for assessing the effects on PCDDs/PCDFs on Fraser River sockeyesalmon (see Section 5.4.3 for more information).Polybrominated diphenyl ethers (PBDEs) and Polybrominated biphenyls (PBBs) - Twoclasses <strong>of</strong> brominated hydrocarbons are typically included in the group <strong>of</strong> chemicalsthat are termed brominated flame retardants, including PBDEs and PBBs. Thesechemicals are structurally similar to PCBs and have similar behaviours when releasedinto the environment. Both groups <strong>of</strong> substances are hydrophobic, fat soluble, andresistant to breakdown (De Wit 2002). Hence, PBDEs and PBBs tend to bind tosediment and soil particles, accumulate in biological tissues, and persist for extendedperiods <strong>of</strong> time in the environment (De Wit 2002).Few data were located to evaluate the toxicity <strong>of</strong> PBDEs or PBBs to salmonid fishesin aqueous exposures. However, the data available on other fish species suggest thatthese classes <strong>of</strong> chemicals are toxic in short- or long-term exposures. For example,Mhadhbi et al. (2010) reported 96-h median LC50s <strong>of</strong> 14 to 30 µg/L for larval turbot(Psetta maxima) for two PBDE congeners (PBDE-47 and PBDE-99), with lowestobserved effect concentrations <strong>of</strong> 1.6 and 3.2 µg/L established for these substances.Hatching success was reduced at concentrations higher than those that caused larvalmortality (Mhadhbi et al. 2010). Exposure to these contaminants also resulted inabnormal skeletal formation and increased incidence <strong>of</strong> pericardial oedemas in larvalturbot. The types <strong>of</strong> effects observed and the concentrations <strong>of</strong> PCBEs that elicitedadverse effects in turbot were consistent with the results <strong>of</strong> earlier aqueous-exposurestudies conducted on zebrafish (Danio rerio; Lema et al. 2007) and killifish (Fundulusheteroclitus; Timme-Laragy et al. 2006).The results <strong>of</strong> feeding studies demonstrate that dietary exposure to PDBEs canadversely affect fish. For example, Muirhead et al. (2006) reported reproductiveeffects in Japanese medaka that were administered a single dose <strong>of</strong> PBDE-47,90